Rollbackers are users in training, which means they are given the rollback right in order to prevent vandalism. After a period of time, it is decided whether or not they should become a moderator / administrator.
Below is a complete list of Wikitubia's current Rollbacker:
Becoming a Rollbacker
In order to become a rollbacker, a bureaucrat must make you one. You must be an active contributor and also help fight against vandalism.
What Rollbackers can do
Rollbackers can undo edits in one click. Regularly, undoing an edit will take multiple clicks. But with rollback, it will automatically undo recent edited user's edit in one button, and the recent changes history.