I think Roach confidence on Pac was based on what he's seen 1st hand on the Gym up to the Ring. In the Gym Pac Spars with Vasquez, Guerrero, Valero, Linares, Ortiz, Antillon, Lazcano, Sta Cruz, Khan etc in the Past. This are top notch guys with p4P talents but you never heard any stories that any of those guys Owned pac in sparring. All you hear is Pac just toys with them.
Then there's the Mitt Practice with Roach. Roach knows how much force was coming from Pac fist compared to the rest his top guys in his Stable. He was quoted in the past saying Pac hits like a Middleweight, That he has more pop than DLH(Already proven). So Roach knows How extra ordinary Pac's Power is. I think these are the reason Roach was so confident to take all these big Fights for Pac.