Garcia's men have suffered defeats to title rivals Juventus and Napoli, in addition to successive losses against Bayern Munich in Group E of the UEFA Champions League, during a tough spell.
However, they are still only three points behind leaders Juve in Serie A, while their Champions League fate remains in their own hands.
"We need to play like Roma, with aggression and enthusiasm," the Frenchman told a news conference on Saturday.
"We have belief. I see my players on a daily basis and they've trained well.
"In my mind Roma are on the same track as last season, but we're playing more matches. Our beliefs haven't changed one jot. I don't think we've dropped off physically.
"I believe in my players and with them we can achieve great things this season.
"Our playing style has brought results; one game is not going to change my beliefs. The lads are up for it, it will be tough but we'll do everything to win."
