I would say New Hampshire Red but it really is funny. He does look like a mixture of breeds. Looks like that RIR behind him (pictured above) could also be a Roo.
Here is a pic of my RIR, She came from MPC and I too believe she is mix something.. she was very shy at first, but with a lot of hands on.. and hand only feeding in the am, her and 26 other cicks have all become very people oriented.
I don't think shes 100% RIR because she has a bit of barring on her wing feathers. The light color of her head is chick down and is starting to be replaced by real grown up feathers.
Her and the other RIR have looked so much like little pretend eagles that we have name one Philly and this one is Henlee