You should be able to reset all rosters. If not:
I assume you don't have Xbox live? If you do, just log in and start a on-line game, and it will auto download updated rosters, with all the changes you wanted.
If not, can't you just go to the main screen under rosters and trade the people there?
Lastly, if none of these are and option or work, start a franchise and be all the teams. You can trade between teams without any problems.
Hope this helps.