Banebot wheels are awesome for roller claws. Make sure to get Shore 30A ones for maximum grip. Also use Banebots 550 geared somewhere in the range of 26:1 depending on wheel diameter.
http://banebots.com/c/WHB-WS
Here is a video of our bot using them, along with a 360 view of our claw.
http://www.youtube.com/watch?v=SZ7jTKJNLzg