You've created a Sling ID to post on this forum. Give your roommate that Sling ID (i.e. email address, not your forum handle) and password and have him/her set up the Slingbox using that Sling ID. Once the Slingbox is set up, you can sign into a Slingplayer app or Slingplayer for Desktop.
And if you want to make sure your roommate isn't using the Slingbox, change the password to your Sling ID.