This sounds more like a nickname, and it doesn't have a very mature or sophisticated sound to it. It's a bit of an amusing name, too. I would probably laugh if I heard a parent shout ''Rollo, come here!''
I cannot think of this name without envisioning a rolly-polly person, having seen the animated film version of "101 Dalmations" (Rolly was one of the puppies, and a rather pudgy little one). Please have mercy on your child and don't name them this.