The former Villarreal striker is recovering from a knee injury sustained in last month's 1-0 win over Livorno.
Further scans have since revealed that the Italy international, whose career has been plagued by knee issues, does not require surgery.
Rossi witnessed his team-mates reach the Coppa Italia final with a 2-0 win over Udinese on Tuesday, securing a 3-2 triumph, with club president Andrea Della Valle dedicating the success to the 27-year-old.
And Rossi is confident he will recover to feature in the final against Napoli in May.
"I have been told of the dedication from Della Valle. It brings me so much pleasure," Rossi told Firenzeviola.it.
"I was thrilled to see the semi-final on television. I spoke with some of the directors on this extraordinary achievement.
"And when I return, which I hope will be as soon as possible, I want to repay all that confidence that Fiorentina have had in me.
"With patience, hard work and dedication I will return to play.
"Where will you see Giuseppe Rossi come May? On the field, at the (Stadio) Olimpico."
