Hmm, for the rosters, create the players ingame, then create a new team (with a DBF editor), for a tutorial look
here.

Then edit the PLYRPKG of each player, the TEAM and ORIGTEAM columns (it should basically be the same number), and finally edit the appearance.dbf (search for PLYRID of the player and it'll be easier to find the player you want). I hope you understood what I said because I'm not 100 % sure... But originally it should be like NBA Live 2004.