I don't keep rosy boas, so can't give advice on proper substrate for them.
I am NOT a paper towel person. These are snakes, not snadwiches. I'm not a butcher paper or newspaper guy either. It just looks so boring to me and provides nothing to the animal. It's easier for the keeper, sure, but snakes are so darn easy any way.
I prefer more naturalistic enclosures where I can at least somewhat mimic their natural environment.