This idea needs to be credited to nycmaire, I'm just posting her idea as a form of distribution.
Team Rosalie is a team to discuss a character that we love and support. It is not exclusive: that is, it allows its members to belong to other "Teams". Unlike Team Edward, Team Jacob, and Team Bella, you don't have to choose Rosalie as your favorite character, though many of us do. (I personally can't, only because I like too many of them:D). It is, as nycmaire stated, a form of club, where we can discuss, show support, and admire Rosalie.
Go Team Rosalie!