The first few times I rode my gelding (with a snaffle bit), he was doing quite a lot of head tossing when asked to do what he didn't want to do. For example, stand still when he wanted to continue home. I was told that he was ridden by children that allowed him to pull the reins from their hands with the head toss. He has never been able to pull from my hands, but it doesn't mean he still doesn't try. During these rides he would chew and chew on his bit.
My trainer wanted to try him in a hackamore and he has done very well with it. However, he tries to get the shank in his mouth every chance he gets. I literally spend most of my ride keeping it out of his mouth. He will also try to get rein in his mouth to chew on, or when I am bridling him, he tries to chew the chin strap, etc. If I just hold him with a lead rope, he stands pretty quietly, but if there is anything even near his mouth, he wants to chew. He is obsessed with chewing on things.
My question is, should I use one of those bits with a roller? Should I give him a bit to play with (being that it seems he enjoys it) or should I try to discourage this behavior? He takes the bit easier than any horse at the ranch. It's like he's excited about it! I've been told not to let him chew on things as it ruins them and I certainly don't let him do that. However if happily chomping on the bit is what he wants, do I let him?