The home side took the lead when Rossi made good use of a corner to find Rodriguez, who headed home in the 30th minute.
The Serie A outfit could have gone 2-0 ahead towards the end of the first half, but Massimo Ambrosini wasted a good chance as his shot on goal was saved.
Ferreira missed out on the chance to equalise shortly after half time when Manchester United loanee Bebe broke free, only for the attacker to send his effort tamely wide of the post.
Fiorentina cemented their lead in the 67th minute when Borja Valero set up Ryder Matos with a cross, allowing the striker to finish and put his side into a 2-0 lead.
The home side's victory was finalised after great play from Alberto Aquilani allowed Rossi to add his side's third in the 76th minute with a sublime finish, which ended up in the far corner.