The Viola boss spoke of his delight at securing the striker's transfer but stressed that his side needs to remain fully-focused on its game against Pescara.
The Viola currently sit third in Serie A, nine points behind leaders Juventus, and their coach believes that their latest signing is a coup that shows the club is heading in the right direction.
"Giuseppe Rossi is a great signing. He's a fantastic talent, and hopefully we'll have him fit again before the season is out," Montella told Viola Channel. "It shows that the club is working well on the transfer market and can convince the right sort of player to join us by offering them the right motivation and incentive.
"Rossi could have chosen any number of clubs, and the fact that he opted for Fiorentina in the end makes me feel proud."
Rossi, who has been on the sidelines since tearing his anterior cruciate ligament against Real Madrid in October 2011, is expected to return to action in March, but Montella stressed that the real focus needs to be on the next game.
"We have to think about Pescara now," Montella said. "They're a team that knows how to defend well, with seven men at times, but when they win the ball back they can hurt you."