Roy Halladay: I NEVER Cheated ... Roger Clemens Can't Say That

Roy Halladay is firing back at his hero-turned-nemesis, Roger Clemens ... telling TMZ Sports he wasn't a cheater, and Clemens is just trying to deflect.

The former Blue Jays teammates started warring because Halladay tweeted "No Clemens no Bonds" -- due to their alleged steroid use -- the night before the latest Hall of Fame inductees were announced.

Clemens responded by accusing Halladay of "using amphetamines" when they were in Toronto. Roy flatly denies it, and points out Roger is the only person to ever accuse him of using illegal drugs.

“I grew up a huge Clemens fan. Getting to play with him, he became a role model. When I heard that he had cheated, it was like finding out Santa Claus wasn’t real all over again to me.”