The Viola go into the encounter at the Stadio Artemio Franchi having drawn their last two league games, their goalless result at Lazio last time out leaving them in sixth place in the standings - seven points adrift of third-placed Juve.
"We are coming off two bad draws at home to Cagliari and Parma," Rossi told the Gazzetta dello Sport. "We need to win three points.
"I tell you what - we win in the league and Juventus beat Real Madrid at the Bernabeu (in the Champions League on Wednesday). And everyone, more or less, will have a reason to smile!"
For the first part of that scenario to happen, though, Rossi knows his team will have to nullify the threat of Juve playmaker Andrea Pirlo.
"If you are able to limit the influence of Andrea Pirlo then you have a nice advantage," he said.
The Old Lady, who are aiming for a third successive Scudetto, find themselves behind Roma and Napoli in the table despite having won six and drawn one of their seven league games so far.
However, Rossi believes Juve remain the team to beat in the title race.
"Juventus are in pole position, but the others are knocking on the door," the former Manchester United and Parma man said.
Fiorentina held Juve to a goalless draw last season in Florence and Viola coach Vincenzo Montella hopes his team can do better this weekend.
"We want to win," he said. "We know how important this game is for our fans and we hope we can satisfy them.
"We are preparing to do better than we did last year - even though we did quite well against a team like Juve."
Rossi, who has scored five goals in seven games for the Viola, will lead Fiorentina's attack.
Juve, meanwhile, head into the game on the back of a morale-boosting 3-2 home victory over AC Milan in the last round.
The result extended their winning run to four games and lifted Antonio Conte's side to third place, two points behind Serie A leaders Roma.
"When the fixture list was drawn up, everyone said we would have a really tough start," Conte said. "I would have been more than happy with six wins and a draw by this stage."
A win on Sunday would be a big boost in confidence for the Turin giants ahead of next week's Champions League game against Real Madrid in the Spanish capital.
Juve will be without striker Fabio Quagliarella, who sustained a muscular injury this week and will be out of action for 20 days.
Carlos Tevez will lead Juve's attack alongside Sebastian Giovinco.