Roy couldn't hold players back even if he wanted to. Kids and parents have direct feedback from the NBA and they make their own decisions. He just hasn't had OAD talent.
The simple truth is all the players you guys pointed to that had high rankings and "should" have or "could" have gone didn't impress the NBA and weren't going to get drafted high. Those rankings did not reflect NBA readiness, and it's unlikely playing anywhere else would have changed that.
It's rival coaches and fans who keep trying to play the "he holds you back" card... and, granted, with some success. But that still doesn't make it true.