The cooling fins on the roller brake on my Nexus IGH are about the same size as a disc brake rotor. I wonder if they actually overheat worse despite technically being a type of drum brake:


That said, I like what someone else said re adding any third brake to the front. Weight shifts front when stopping anyway. Getting a new fork with disc brake mounts is also cheap and easy. I got a carbon rigid fork with disc mounts for $65 the other day.