That Yanagi voted for Izumi instead of Akari is interesting and probably proof that she's not the wolf (and because the manga is ongoing lol). I wouldn't be surprised if Izumi really is the wolf
edit: Actually, if we're adding roles into this game, Izumi might be the madman and the president the wolf? The not-twins are probably the lovers given how interconnected they are.
One thing that I noticed straight off the cuff that hasn't been too relevant as of yet is the fact that the characters are named one through ten.
ICHIji Yuki
NInomiya Midori
MIshiro Aki
YOtsuya Aoi
ITSUki Akari
ROKUdera Izumi
NANAshi Shion
YAhara Sakura
KUzumi Ai
JUUjou Yanagi
And then there's the two wildcards:
Ouji Suzu & Shimura Touko
I've yet to really figure out what any of this means (I've actually only skimread the untranslated chapters), especially what relevance Suzu's first name being Prince and the "Shi" in Touko's name referring to some kind of samurai or knight.
So far, actual werewolf roles are sort of up in the air. I think moreso than their roles following the rules of the game, each of the girls represents one of the traditional roles - the not-twins being lovers as you said.