I agree that the movie was bad, but I don't think one can pin it all on Chris Roberts. In my mind the biggest problems with the movie were:
1). Freddie Prinze, Jr couldn't act his way out of a paper bag. They cast him because he was a "hip young popular actor", but he can't act, and he wasn't nearly popular enough to justify his acting. It's a shame, because I liked the performances of some of the other characters (Paladin, Angel, and Lilliard's Maniac especially).
2). Bad editing of the script. Some gaping plot holes and inconsistencies. It's been a while since I saw it, so I don't remember many of them, but if people want to discuss I'm sure I could dredge them up.
3). Too many cliches. Again, a problem with the script.
4). The whole mythical powers thing did bug me. It wasn't just being able to do math well, because, as someone pointed out, a number of people can do math well. Movie Blair was the only one who could do this fancy, manual jump thing, not because he was mathematically gifted, but because he was part Pilgrim (by the way, I thought the whole invention of the Pilgrim thing was horrible--where did that come from? It's not in any of the games, although I confess that I haven't read any of the novels...).
The movie's concept and visuals were very impressive, and the directing was well done, but the other problems did it in.