In case there was any question, it appears Bruce Miller has in fact transitioned out of his fullback role. He is officially out of the running backs room.
Upon showing up to offseason program, #49ers RB coach Tom Rathman told Bruce Miller he no longer had spot in RB room. He was a tight end.
— Matt Maiocco (@MaioccoCSN) May 17, 2016
Miller had previous experience lining up in different positions besides just fullback. That provides important experience for a role that goes beyond just "tight end." I imagine Miller will operate in an h-back role that will include splitting out wide, lining up on the line, and occasionally coming out of the backfield.