Federer captured his 10th grand slam title at the age of 25 on Sunday when he beat Fernando Gonzalez in the Australian Open final but Roche believes the best is yet to come.
"Roger is like a good red wine, he's getting better with age," Roche told reporters in Australia.
"I think his big years will be when he is 26, 27, 28, as that is when he will be both mature and at his physical peak. I think he will become a better player in many respects.
"It's a challenge for those trying to stop him. But they are playing against a man who will probably enter tennis history as the best ever."
Federer is quickly closing in on Pete Sampras's record of 14 grand slam titles, but his immediate aim is to win the French Open -- the only majorthat has eluded him so far.
The Swiss master lost last year's Paris final to Spanish world number two Rafael Nadal but Roche said Federer was only just finding his feet on clay.
"If Roger wins the French Open, that would complete a lot of things -- that could be the most important thing for him right now," Roche said.
It only seems like a matter of time until Federer passes Sampras's tally of 14 majors but the world number one is already eyeing an even loftier goal.
Only five men have won all four majors in their careers while just two, Don Budge (1938) and Rod Laver (1962, 1968), have completed the coveted Grand Slam by winning them all in a single year.
"The Grand Slam would be the ultimate," Roche said.
"I had always thought it would be impossible for anyone to do the Grand Slam again after Laver -- and then I met Roger."