There has been a little bit of confusion so far this game as to what all the roles do.
The Sheriff gets to ID once per game day. The ID comes back as either "mafia" or "not mafia". The serial killer, doctor, etc... come back as "not mafia". The godfather is also a tricksy bastard and escapes detection.
The Doctor submits a save once per game day. If the doctor is saving a person who gets hit by the mafia or the SK, then that person survives and I will drop huge clues in the scene as to who the culprit is.
The Serial Killer kills someone once per day. They are on their own team and only win if they are the last being standing.
The Godfather kills someone once per day, and can escape detection by the sheriff.
The Mafia are the bad guys, and take over for the godfather if the original one dies. They do not gain detection immunity, however. Their main purpose is to make sure townies get lynched and just basically be sneaky bastards.
The Suicide Bomber is a role that only me and Ras have experimented with. We have changed it a bit since last game. In this game, the suicide bomber does not submit a daily SKID. Instead, they wait until they feel the time is right, and then they PM me a name. As soon as I read it, I will write the scene in which both the Bomber and their target die. This happens outside of the normal timeframe of the game. If I get the PM at 3am, I will write it and post it then. If the Bomber is about to get lynched, I will write the scene and extend the vote so that people can change it to someone still alive, etc...