A list of people I find suspicious:

Suspicious:
Peter Pettigrew
Moaning Myrtle
Cho Chang

Unsure:
Luna Lovegood
Draco Malfoy
Dudley Dursley
Neville Longbottom

Not Suspicious:
Buckbeak
Dobby
Hermione

Anyone else either hasn't posted enough, or I've forgotten them.
Myrtle and Cho are obvious, Peter just is either new, or playing dumb, I think.
Neville and Draco are both claiming Cop, I see. While there may be two, perhaps an insane one, perhaps not, or another role like that, one might also be Mafia.
Luna and Dudley haven't done anything to make me think Mafia, or otherwise, so I'm unsure.
I believe Buckbeak's roleclaim and I'm just not suspicious of Dobby or Hermione.