The Promote/Demote page on the Manage menu (as well as the Roster page) lists the number of remaining starts for each player and the number of reserve appearances. Pitchers display the number of starts and/or relief appearances available.
Pitchers who are used as both starters and relievers in MLB can be used in BBM the same way, but when a pitcher is locked into a start he cannot be used as a reliever.
Reserve appearance are also listed -- these are games where a player came off the bench to play.
Players with no appearances remaining will cannot be placed in the team's starting lineups or starting rotation.
Note: Players with no appearances remaining should be demoted to the Minors Roster if the manager wants to build up the number of available appearances. Active benched hitters who appear in that night's MLB game can be selected by the game to be used as a reserve. Active benched pitchers who make a relief appearance in that night's MLB game can have that appearance used in BBM.