I decided that while I had the roof in the shop I would go ahead and prime it for painting later. I did final sanding with 320 grit sandpaper and then primed it with AlexSeal primer. The primer was thinned with the proper thinner and applied with the proper roller as per the AlexSeal directions. They claim that the roller texture would not show, but when I finished applying the primer, the rough roller texture was obvious. I was quite disappointed, but when I returned an hour later it had miraculously disappeared! Hurray! I am now optimistic and encouraged that the AlexSeal product will provide a good final paint finish for the boat exterior.