Learning to Crawl

We have been trying to teach Camden to crawl. So far, he hasn't been very interested in crawling. He prefers to roll wherever he needs to go. He has gotten pretty clever, too. If we put a toy out of reach, he pulls the rug or blanket to him to get the toy. I recently removed the rug & blanket in the play rooom to encourage him to crawl. He gets so mad when he can't reach a toy! He will try to reach the toy for about 2 seconds, then throw his head down on the floor and start screaming! It's pitiful and funny at the same time. I don't know if he will figure it out or just skip crawling.