This sounds awesome, and I'd love to be a part of it. Ever since I heard about RBN I've been really excited and I've wanted to find a way to get involved. Helping with peer review would ge a great way to get involved and I'd love to do it!
I play Rock Band on Expert for all instruments, most of the time. I do, however, occasionally have to pull down to Hard for really difficult or really fast songs (although not for vocals, I can play all songs on Expert there). As for how much time a week I play, I admit it's not generally very much, but that is simply the artifact of not having enough money to purchase any new songs. Should I be selected for this, I would do my best to peer review as many songs as I possibly could in order to really help this community out.
Beyond simply Rock Band, I also have a musical background. I've been in a post metal band playing guitar, bass, drums, and vocals, and I've recorded with that band in the stuido, as well as setting up a basic recording set up (very basic, just an interface and some dynamic mics that are super cheap) and recorded the band with that. I feel all these things make me a good choice to peer review.