Thanks for your answers. There definitely is room to roost, and I've seen the rooster flap his wings. There doesn't seem to be any mice or anything that would disturb him. The roosts seem to be sturdy, but perhaps he is trying to gain his balance.
This is the dominant rooster in my flock and is always extremely active. When I peek into the coop at night, he immediately stands up on the roost. I am glad to hear that others have roosters that crow constantly. I doesn't bother me really, but I am amazed at how often he crows. If I wake up at 3 AM or so, I hear him crowing. He crows during the day almost nonstop, as well.