Carlos Tevez sprayed the crowd with imaginary bullets. The Juventus striker had already wounded Fiorentina's supporters, scoring against their team at the Stadio Artemio Franchi, but now he was doing them an even more grievous injury. By celebrating his goal in this way, mimicking a machine gun with his hands, Tevez was imitating Gabriel Batistuta – one of their most beloved former players.

If there was any doubt that this had been a deliberate act, then it was eliminated three minutes later, when Paul Pogba did the same. After putting Juve 2-0 up with a close-range volley, the midfielder strafed the stands with his own fictitious firearm.

Such gestures served to remind Fiorentina's fans of a painful truth: their team had not won this fixture since Batistuta last won it for them. The Viola's most recent home victory over Juventus had arrived on 13 December 1998, with the Argentinian scoring the game's only goal. Batistuta was so overcome back then that he forgot how guns functioned, and instead launched into a furious, fist-pumping, guitar solo.

The celebrations in the stands were even more delirious. A fierce rivalry exists between these two clubs, dating back to at least the early 80s. Juventus famously pipped Fiorentina to the scudetto on the final day of the 1981-82 season – beating Catanzaro 1-0 courtesy of a Liam Brady penalty while the Viola had a goal disallowed in their 0-0 draw with Cagliari. Conspiracy theories abound. "I saw [the then Juventus president Giampiero] Boniperti eating peanuts in the stands," claimed the film director and Fiorentina fan Franco Zefirelli at the time. "He looked like an American mafioso."

Incidents since have deepened the animosity. In 1990, Fiorentina were forced to play the 'home' leg of their Uefa Cup final against Juventus in Avellino – an area where the Bianconeri enjoy great support – and duly lost 3-1 on aggregate. Last summer Juventus persuaded Dimitar Berbatov to renege on an agreement to join Fiorentina and sign for them instead. He subsequently ditched both clubs and went to Fulham, but the Viola remained furious at being gazumped.

Fiorentina, though, might ultimately have been better off without him. In lieu of Berbatov, the club have since acquired Mario Gomez and Giuseppe Rossi.

The latter was, of course, still recovering from back-to-back knee ligament injuries when he arrived from Villarreal for €10m plus bonuses in January of this year. He had not played in 15 months, and would need several more before he could even think of a return, but the potential returns were significant. Rossi had scored 32 goals in 52 games in his last full season for the Spanish club.

He had, indeed, been coveted by Juventus. "A few years ago negotiations [with the Bianconeri] got to a very advanced stage," Rossi told Gazzetta dello Sport last week. "But then Villarreal got into the Champions League and said nobody could leave."

Instead, Rossi found himself lining up against Juve this weekend. For 66 minutes his impact was limited. Rossi is, by his own admission, happier playing off another striker than leading the line – as he has been required to do in Gomez's absence. Despite working hard for the team on Sunday, neither he nor his team-mates had created many goalscoring opportunities of note, before Mati Fernández went down under a challenge from Kwadwo Asamoah in the area.

The referee, Nicola Rizzoli, pointed to the spot and Rossi stepped up to convert. There was no machine-gun celebration here. Juventus were about to be pierced by the rat-a-tat-tat of three more goals in breathtakingly quick succession.

First Rossi surprised Gigi Buffon with a snap-shot from the edge of the area that snuck past the goalkeeper's outstretched palm. Joaquín added Fiorentina's third just a few moments later, taking a pass from Borja Valero and slipping it in at the back post. Rossi then completed the scoring in the 80th minute with a glorious first-time effort to cap a lightning counter-attack. Final score: 4-2.

Even to the most optimistic Fiorentina fan such a turnaround must have seemed implausible. Juventus had never before conceded four goals under Antonio Conte. And Rossi had never scored a professional hat-trick.

The forward has now scored eight goals in as many games this season. Fiorentina's co-owner, Andrea Della Valle, would insist afterwards that he had never viewed signing Rossi as any kind of gamble, but even he cannot have anticipated quite such immediate returns.

Credit is due to Vincenzo Montella, the Fiorentina manager, who said on the eve of the game that his team's primary objective was to play entertaining football – even if that was not the best route to winning titles. Rossi's admiration for his manager is clear. He has said that the No1 attribute he would like to take from Montella was "the courage he had [in his playing days] to always try something special. Splendid overhead kicks, volleyed finishes: he was never afraid of messing it up".

Rossi's own confidence seems to grow by the week, and will doubtless have been boosted further by his return to the international fold. A 16-minute cameo against Armenia on Tuesday represented his first appearance for Italy in just over two years, but already considerable hopes are being invested in him. "With a Rossi up front, Italy usually win the World Cup," quipped the Gazzetta journalist Paolo Condò on Twitter.

The player himself is not thinking that far ahead, insisting to reporters that he was only thinking one game at a time. And Sunday's result was certainly worth celebrating in its own right. Both Della Valle and his brother Diego came down to the changing rooms afterwards, bringing bottles of champagne to share with the players.

"For our fans this game alone is like winning a trophy," said the defender Manuel Pasqual, although the result also had positive implications for Fiorentina – keeping them in touch with the chasing pack. After last season's near-miss, this team is intent on challenging once again for a Champions League place.

Fiorentina were not the only ones, however, to benefit from such a result. Juventus's defeat allowed Roma to remain five points clear at the top of Serie A, following their own remarkable 2-0 victory over Napoli on Friday.

The match was originally scheduled to take place on Saturday, but was moved in order to avoid a clash with a planned protest in Rome against the installation of a new high-speed railway line. It had been mooted that the fixture could simply be flipped to Naples, switching dates with the return fixture later this season, but the Roma manager, Rudi Garcia, was strongly against any move that might undermine his team's early-season form.

His resistance was vindicated by another resolute performance from his team, who controlled the game despite losing Francesco Totti and Gervinho to injury. In the captain's absence, Miralem Pjanic took over the set-pieces and duly opened the scoring with a superb free-kick on the stroke of half-time. He later added the second from the penalty spot.

It was quite the week for Pjanic, who helped Bosnia to qualify for their first-ever World Cup on Tuesday, and it has been quite the season for Roma, who have now won eight consecutive games. Juventus are the only other team ever to have achieved such a feat in Serie A – doing so in 1930-31, 1985-86 and 2005-06. They won scudetto on every occasion, although the last of those was taken away as a result of the Calciopoli scandal.

Perhaps even more remarkable than Roma's points tally is the fact that they have achieved it while conceding just a single goal. A timely intervention was required from Daniele De Rossi on Friday, clearing off his line after Morgan De Sanctis could only half-block Goran Pandev's effort. Lorenzo Insigne really should have done better than hit a post when through on goal in the first-half, but those were the only real chances that the visitors fashioned.

Garcia played the win down afterwards, describing it as "a little bit of a Phyrric victory, given the injuries to Totti and Gervinho", but perhaps more revealing was the manager's decision to give his team three days off as a reward. That is a luxury that none of his rivals – each of whom have European games to worry about this midweek – could afford.

While Roma are relaxing, Juventus must gather themselves quickly for a Champions League trip to Real Madrid. After drawing at Copenhagen and at home to Galatasaray, the Italian champions are already under pressure in Group B.

But they will at least have Rossi cheering them on this Wednesday. "We'll win the league game, and then Juve can beat Real at the Bernabéu," said Rossi last week, when asked to make a prediction for Sunday's game. "That way everyone has a reason to smile."

Conte might not have signed up for such a deal beforehand, but he would certainly take it right now.

• One team that I have really not expended enough words on in this column – as a few of you have rightly pointed out – is Verona. They recorded their fifth win of the season on Sunday, moving up to fourth place after recovering from a goal down to beat Parma 3-2, and have looked so far like a model of what newly promoted sides should aspire to be – marrying the experience of veterans like Luca Toni and Massimo Donati with the promise of some authentically exciting youngsters like Jorginho (who scored twice from the penalty spot on Sunday) and Juan Iturbe. The manager Andrea Mandorlini has brought the different elements together expertly.

Sadly the team's fans have won headlines for the wrong reasons at times, brawling with their Bologna counterparts before their game at the Stadio Dell'Ara just before the international break, but on the pitch they have been tremendous. They go into next week's game away to Internazionale looking down at the Nerazzurri in the standings.

• Gian Piero Gasperini seems to be making his mark already after returning to Genoa. The club collected four points from their first six games of the season under Fabio Liverani, but have matched that tally in just two games since their former manager returned.

• At last, Sassuolo have their first-ever top-flight win, leapfrogging Bologna this weekend with a 2-1 defeat of the Rossoblu. Theirs was not a especially compelling performance, and they needed a moment of inspiration from Antonio Floro Flores – who scored their second goal with a fine, low shot from 20 yards – to get them across the line. You have to start somewhere, and for the first time all season, Sassuolo's players could wake up this morning knowing that their team were not bottom of the table.

• The first match of the Erick Thohir era at Inter was certainly an eventful one. The Nerazzurri had their goalkeeper, Samir Handanovic, sent off after five minutes, watched his replacement, Juan Pablo Carrizo, save the ensuing penalty, fell behind anyway a quarter of an hour later, equalised before half-time, conceded again early in the second, scored twice to take the lead and then blew it all by giving up a goal from a free-kick in the 90th minute. The more things change, the more they stay the same for Pazza Inter.

• Milan have won three games so far this season in Serie A, and two of them have been settled by goals from Valter Birsa. Do what you will with that information, but his goal against Udinese this weekend was certainly easy on the eye.

Results: Atalanta 2-1 Lazio, Cagliari 2-1 Catania, Fiorentina 4-2 Juventus, Genoa 2-1 Chievo, Livorno 1-2 Sampdoria, Milan 1-0 Udinese, Roma 2-0 Napoli, Sassuolo 2-1 Bologna, Torino 3-3 Inter, Verona 3-2 Parma