How's he controlling the shuffle? You'd have to do some pretty physically tricky card manipulation to make them align while trying to look like a normal shuffle. I mean, it'd look pretty funny to the other players whether he was riffling through the cards slowly enough to control which card fell where, or just shuffling it over and over and over until he got it to where it would draw him the royal flush. It's not something precog alone -no matter how strong- will let you do in one go.
Seriously. Try taking a deck of cards, and look at it face up so you can see what the cards are. Now try to shuffle them so that a royal flush is on top. (Or, if you prefer, so that each card needed is set at a specific interval from each other so that in a game with X players, when you deal out cards one per person five times that you end up with that hand.) Without slowing down as you let the card tips flip off your thumbs.