I'm not sure if the rockers are different, but the convertibles will have a nice heavy piece of C channel running the inside length of the rocker.
When I got my RR, I had to do a repair to an area from a previous collision. The outer rocker was cracked. When I cut it away, I saw that the inner rocker had been cracked and repaired by welding a bolt in to take up space.
I cut the bolt out and welded in fresh metal. Then did a repair on the outer rocker.