The Pittsburgh Steelers superstar tells TMZ Sports he's hopeful one day that'll be possible ... saying if his inspiring story ever hits the silver screen -- he wants Dwayne Johnson to play him!

"I need somebody to knock that role out of the park," Conner tells us.

James has put on some serious size this off-season (for real, check out his Instagram, dude is buff as hell) and he does have some tats ... so he says The Rock would be perfect for the role.

"I know he's getting up there, but ..." Conner says.

Of course, 25-year-old James definitely has the story worthy of a starring role from The Rock ... he famously kicked cancer's ass to become one the best running backs in the NFL.

For now, though, Conner's life is set for book form only ... the NFL star released his "Fear Is A Choice" memoir this week, and he says he hopes it'll help others overcome adversity.

"You have to kinda appreciate the dark days in order to move forward and have joy in the future," Conner says ... "I just want people to believe in themselves and realize how mentally strong that they are."