Here is what Farout guy said:
Sign into your 360 profile, load up 08
Load 08´s main profile and turn autosave off (this will make sure the roster doesn´t change)
Go into my nhl 08 save/load/delete
Delete all of the saves that are rosters (Roster1, Roster 1, Online Roster1)
After this is done, Restart your xbox (it needs to register that they are gone)
Again load your nhl 08 main profile
Go Online and play a quick ranked shootout *Actually play and finish the shootout (The game needs to actually load the rosters)
After the shootout it should take you to the main menu
Go into my nhl and save the roster as "ROSTER 1"
Then after it saves just load the roster everytime before you play 08 online.
J´ai un peu traduit mais j´ai pogner sa sur le nhl 08 forum et pour moi sa la marcher 