There are 3 Mafia.
I will not list the roles that are available but there is nothing too crazy I promise.
With 13 Alive it takes 7 to lynch
(13) Everyone - Not Voting
Cool! Okay, here are some thoughts on roles and such:
We have 13 people minus 3 mafia. That leaves 10 people. I would guess that at least half of them--maybe exactly half--have to be vanillas. They don't have to be, I suppose, but that's my guess. That leaves 5 people with unspecified special roles. Also, I assume one of the mafia is a specialty role, like Mafia Rolecop.
Jailkeeper, Doctor, Cop: These are the roles that have been used in the other games. I think people are pretty familiar with them. I doubt we have all 3 in the game--they are rather strong--but possibly 2 of them. There are also twists on them, like the Mad Doctor, who kills his target 50% of the time rather than saving it. Who knows if Insomniac went that route.
Doublevoter: This is a weak-ish, but cool, special role. The Doublevoter gets to cast 2 votes during the lynch. Depending on how Insomniac structures it, it can be really easy to figure out who the DV is, making him sort of an obvious mafia target, but... it's interesting.
Shield: Or any other role where the person gets one free "life" in the night. We might have something like that.
Lovers or Couples: I've played with these people once. There are 2 of them. They know who each other are. When one dies, they both die (either during lynch or at night). Other than that, they are just townies. The good thing for them is that they have someone they know they can trust, so they have more info right off the bat. The problem for them is they really have to watch out for each other, and if one says, "I am one of the Couple!" it's really easy for the mafia to score a free double kill in the night.
Serial Killer, Mole, WhatHaveYou: I doubt we have this, if there are truly 2 mafia. 4 killing bad guys seems like a lot. But maybe! These people are part of their own faction and generally have to survive to the end. Neither the mafia nor the town can win until the Killer dies.
Vigilante: This is a townie night killer. He gets to kill someone in the night. He wants to go after people he suspects, obviously, or not use his power. If we have 3 mafia and no other killing role, this might be a logical inclusion.
Those are some of my thoughts. I am sure there are like a million other possibilities.