Boxer Kid Chocolate -- Lands First Movie Gig ... I'm Playing Roger Mayweather!!!

Boxing champ Peter "Kid Chocolate" Quillin is making his silver screen debut next year -- as none other than the original Black Mamba himself Roger Mayweather ... TMZ Sports has learned.

Quillin tells us he auditioned, and landed the small role in an upcoming flick entitled "Bleed For This" -- a true-life story centered around the life of world champion boxer Vinny Pazienza, played by "Divergent" actor Miles Teller.

"Only Roger Mayweather can be Roger Mayweather," Quillin says ... "What I tried to do is bring a fighter's mentality to his character."

The 31-year-old champ says the hardest part of the job was nailing down the fight choreography -- since he's not used to scripting out his moves in the ring -- but says there's one part of the gig that came naturally.

"I remembered all of my lines. I didn't f**k up."