Latest Update: 2012/06/27
A new official roster update for NBA 2K12 is now available. It features final 2011/2012 season rosters along with updated rotations, moving all injured players back into the active rosters. As always, the new rosters will be downloaded automatically as long as your PC, Xbox 360 or PlayStation 3 is connected to the Internet and your game is up to date with the latest official patch. To load the new rosters, use the Reset Roster function under the Options menu.
PC users who would like to manually update their game may download here. Please note that as per the NBA 2K Insider, there will be no further roster updates for NBA 2K12, meaning that the new rookies and offseason trades will have to wait until NBA 2K13.
Start > Run > Type : %appdata%, then find 2K Sports\NBA 2K12\Saves , overwrite all the files.
for XP users: C:\Documents and Settings\[your user name]\Application Data\2K Sports\NBA 2K12\Saves
for Vista or Win 7 users: C:\Users\[your user name]\AppData\Roaming\2K Sports\NBA 2K12\Saves
Then go to NBA 2K12 and load it
NBA 2K12 Online Data for Official Roster Update: