Roulette prediction, like all forms of advantage play, is about a relatively subtle shifting of percentages. You can't predict the exact number, or the exact octant, or even which half the wheel. You may be able to predict that certain numbers are more likely than others, but that is the limit of predictive capability even with a computer.
Brown did a similar thing with card counting at blackjack in another episode. He won some money in a casino and made out that it was due to his amazing memory. In fact an amazing memory makes no practical difference to how much you win at blackjack at all, at least in a single session of play.