Personally I'm not necessarily looking for one that is hollow...that's something slapmaster is working on. I run a Spektrum system so I have no need for a hollow roll-over...just a roll-over antenna in general.
That being said...I've had quite a bit of experience with carbon rods in my days flying stunt kites in teams. It's a bit tricky to find one that is not too stiff, too flexible, or too fragile for use as a roll-over antenna. Many of the carbon ones that are not a wrap splinter very easily and the wraps tend to be too wide in diameter.