Roaming with Xbox 360 requires an Xbox 360 Memory Unit to store your Xbox LIVE profile and your saved games.

While you can, in fact, perform the activity Recover Gamertag from Xbox LIVE to effectively import a fresh version of your profile to your console—or to your friend's console—you should know that doing this endangers your saved games, which reside on your memory unit or Xbox 360 Hard Drive.

With Xbox 360, your gamer profile can exist only in one place at one time, so downloading (or "recovering") it to a friend's system will invalidate the version of your profile that's still on your Xbox 360 Hard Drive, endangering any offline achievements and game saves since your last visit to Xbox LIVE.

Because your profile encompasses elements that are stored on your console and elements that are stored by the Xbox LIVE service, the safest way to game is to move your profile to a memory unit when you hit the road and when you return home.