oh, another thing, if you want to do this with all (or alot) of the teams at the beginning of every dynasty year, you can't just pick a game and play it without simming the games that occur before it. what i do is start with the first game in the week, play it, change the rosters, quit and then sim it. then go onto the next game.
Here's everything i do with the roster changes:
-i try to change the depth charts so that the older players get more playing time, unless the younger players are much better. ex: a senior rated 80 and a soph rated 81, i would play the senior. if it was a senior rated 80 and a soph rated 85, then i'd play the soph.
-i put the good recieving te's as reserve wr's. i still leave them as te's too. when there's a formation that has no te but a bunch of wr's, in real life alot of the great recieving te's split out wide. i put great ones like winlsow as the 3rd wr, and not so great but still good ones as the 4th or 5th wr. this also helps those te's get recieving stats in simmed games.
-i make sure that all reserves are the correct positions. sometimes there are wr's as backup hb's and te's. this does sometimes happen in real life, but not often. what i do is put fb's as back up hb's and te's instead of the wr(unless a given wr has enough size/strength to be an actual hb/te) other ones are wr/hb as corners and safeties. i hate this one. for corners, just put the best non-starting safeties. for free safeties, put the best non-starting corners and strong safeties. for strong safeties, put the best non-starting free safeties and linebackers(with 75+ speed) other positions have wierd subs sometimes, you'll just have to come up with realistic backups.
-i also change starting players as kick/punt returners. you will see some starters as returners in real life, but in the game, it usually always sets the best starters as the returners, leaving them tired on the first play of the drive(or already tired for the return if they're db's)
-in formation subs, i put hb's in formations to best suit they're strengths. i make sure they're best short yardage back is in the goal line, i tight, and other big formations. i also put speedy, catching backs in the shotgun, 3rd downy like formations. obviously, i like to make sure the starting hb is in most of the formations. but if the starter is an 85 ovr, and a backup is only a few points less, but more suited for a specific formation, then i make the change.
-i also make sure the best linebackers are in the nickel and dime formations, sometimes the olb dropped is much better than the mlb, or the other olb. i also check the goal line, 4-4 and 3-4 formations. if the mlb subbed in for those formations aren't as good as a backup olb, i'll switch the starting olb next to him over to mlb, and put his backup in in his place.
-in the 4-4 and goal line formations, i make sure the best safety is in. sometimes there will be a 75ovr fs, when there is a 90ovr ss, or vice versa.
there are quite a few more changes i make, but these are the major ones. you might think this is way to much stuff to do, and it probably is. but if you're a realism nut like me, it will add to the fun-factor and realism of the game. It would also add a couple of extra hours of gameplay, (just editing the rosters) but imo it's very worth it and i recommend doing it if you're an avid ncaa 2004 gamer like myself.