The guaranteed spots in the bullpen, barring injury:

Sergio Romo
Santiago Casilla
Jeremy Affeldt
Javier Lopez
Jose Mijares

And the mostly guaranteed spots in the bullpen, considering he was a) quite good, and b) trusted enough to be on the World Series roster last year:

George Kontos

Which, with five starters, means there's one more spot if the Giants are going to get to a 12-man pitching staff. Ramon Ramirez would seem to have the upper hand. He already knows where the bathrooms are and everything. But he's on a minor-league deal, and I don't think there are any guarantees with him, considering he had something of a down year last season.