He can teach timing, nuances and good defensive habits. If Khan had that he'd be fine. Roach wasn't responsible for Pac's and Khan's good runs, that was Ariza's work on the physical side of things allowing their offence to be more potent. Defence falls under the skill side of things, that's where Roach is meant to be doing his work. Roach is overrated for sure.
Actually that statement "pure offense, and not calm disciplined offense. Not all that well rounded." is true of Pacquiao too. The difference between him and other Roach fighters is he has the speed and explosiveness to make up for it. Give Manny his own credit, don't steal from Peter to pay Paul. He rises above his flaws and remains effective because of his innate talents and his fighting spirit. Not so much because of any "fine tuning" on the part of his trainer.
And he's taught all those things. Khan did exactly what Roach told him not to do, and that's why he got KO'd.