Roma will enter their third successive campaign with a different manager, aiming to break into the top five in the Serie A for the first time since 2009-10.
Garcia has bought well in the close-season with Kevin Strootman, Mehdi Benatia, Maicon and Morgan De Sanctis the headline arrivals at the Stadio Olimpico.
"The last few seasons have not gone well, that is clear," De Rossi said.
"What we need is to be reborn. And we start from here, we start with pre-season. It's the preparation for a revival ahead of an important year.
"The club has always been a strong one, even in the years that things didn't go so well.
"However, something has been missing or else we wouldn't have had these seasons that were not too positive.
"We are not missing that much at Roma, but we are lacking a little. What we really need is enthusiasm. We need to put a winning run of games together and start to believe in ourselves again."
De Rossi - who has been a Roma player since graduating from their youth ranks in 2001 - has been used in a variety of positions throughout his career.
And the 30-year-old Italy international says he is happy to play anywhere for Garcia in the new season.
"I do everything. I've always done that. I've never made myself unavailable for a particular tactical solution," he said.
"I've played as a playmaker, a ball-winner, even as a defender. I think that has been under-estimated."
Roma open their Serie A campaign at Livorno on the first weekend of the season, to be held on the weekend of August 24 and 25.
