La Viola trailed 2-0 at the interval but fought back to score four times in 15 minutes, with Rossi's treble and a strike from substitute Joaquin Sanchez enough to end the Old Lady's unbeaten start to the campaign.
Montella has declared that the win has to go down as a highlight of his career, while paying tribute to the home crowd for sticking by his side at two goals down.
He told Sky Sport Italia: "It is certainly among my most enjoyable victories. We looked unable to score, but football is marvellous and the penalty changed the inertia of the game.
"We achieved this despite going 2-0 down, despite losing Massimo Ambrosini, despite Rossi having a back problem. It's tough to score four goals against Juventus, especially with Antonio Conte in charge, and extraordinarily wonderful to do it in 15 minutes.
"I thank the fans, who behaved impeccably and perhaps at times believed in this result more than we did. I considered replacing him [Rossi], but he's a player who can change a game even when he's not well."
The comeback proved enough to earn Fiorentina their first home win over Juventus for just over 15 years.