1) Wondering if it might be possible to get a recap on the special characters besides town and mafia (unless they are to be a surprise).
The most common ones would be:
_Cop: investigate a player at Night to learn if they are Town or Mafia.
_Doc: protect a player at Night. That player won't be killed.
_Tracker: investigate a player at Night. You learn if that player targeted anyone during same Night.
_Watcher: investigate a player at Night. You learn who else that player was targeted by during same Night.
_Vigilante: Town player who can kill at Night. Usually limited (e.g. 2-shot - can only do it twice).
_Roleblocker: target a player at Night. The target won't be able to perform any actions that Night.
_Strongman: Mafia killer who can bypass Doctor protection. Usually limited (e.g. 1-shot can only do it once).
_Godfather: Mafia player who registers as Town to a Cop investigation.
Did I miss anything?
And many more. Some are quite exotic and rarely seen.
Sometimes mods create their own roles, or modify existing ones.
You can find a nice list here:
2) Will you assign everyone a RP (flavor) role or it is up to us to pick one?
I will assign you your faction, any special character role (if any), as well as a name from the Harry Potter universe and some flavour. It's up to you how much you want to roleplay that.
EDIT: Yes, Lifthrasil got it right, regarding closed setup. Meaning no one will know in advance which special roles will be in play.
And let's not forget Siblings. Two town players who if one is killed the other dies too. I Love that special role but it's never seen in practice.