User blog comment:CNBA3/Followers: Recruiting/Dismissing/Rehiring./@comment-4889310-20140820042358

They are able to return to serve you. Once you dismiss them, they head on over to the town hub of the current Act you are in. Simply click on them and selecting the Hire option should do the trick.

Also, just out of curiousity, are you on the PC version, or on a console?