Is Freddie Roach's ability to predict when a ko will happen as impressive as Ali's ability to predict a ko?

I would say yes. The difference between Roach and the rest of us "die hard fans" and "boxing experts" is that he actually knows what he is talking about. Being the trainer, he has access to insights and information about a boxer with whom he has everyday contact with--combine that with his actual boxing knowledge and experience and yes, he could predict a knockdown accurately, not all the time of course, but better than most of us can. The same thing could be said of Ali, the great one.