By popular demand, we recently rolled out iTunes to our users. An unexpected consequence of this was that our windows roaming user profile demands skyrocketed. We're talking over doubling basically over night. Our solution to it was to exclude the My Music folder from the roaming user profile. In general its probably best we don't have user's music collections sitting on expensive enterprise storage. To do this, create a new Group Policy. Drill down to Administrative Templates\System\User Profiles. Enable "Exclude directories in roaming profiles" and set the value to "My Documents\My Music". If there are other folders you'd like to exclude you can add them with a semicolon, eg "My Documents\My Music;Temp".
The good news is that once this policy is enabled, the next time that the user logs off, the user profile will sync without any of the Excluded directories. Even better is that it will remove existing "My Music" folder on the server copy of the roaming profile. Turn on Performance Monitor, setup some counters, and watch the drive space roll in.