That question was asked a long, long time ago and to this day no real specific answer has completly address that aspect of the game.
My theorys are that when using edited rosters you change/alter the way the game makes its pre-program assesments based on how you edited players.
I've seen it work in the original rosters that came with the game after editing some things just don't add up right, its possible the game wasn't intended to prep edited rosters but in actuallity it does in a negative mannor on some training portions or the right training combinations haven't been applied.
Hard to say if I were to use it I wouldn't use edited rosters and stick with the ones that came with the games pre-programed players and rosters.
The only game I play that way is in the EA family and basically thats "Head Coach 09" it was design with that intention in mind and earlier type game basically set up for coaching and micro-managment for that type of game play.
Theres a game you can play online that might catter to your needs for that style of play its call "Quick Hits" and is pretty good.
I'll look into this issue again sometime and see what I can if at all figure out whats going on with it but my gut feeling tells me that rosters per edit just don't work a certain way as the games code see it.
I'm no programmer but some thing are self explained and this appears to be one of them then again you might just have to put together the right combination to get positive results still all in all its cools stuff for micro-managment players wanting to mix it up as far as coaching hands on style.
Rickster101