Do you know what is under the ribbed molding?
It looks like an overlay that NL put there to better distribute the weight of the AC unit, which has been known to sag the roof in NL and BF campers. If it were mine, I would want to leave it there for several reasons: you (or a future owner) may want to reinstall an AC unit, it stiffens the roof for better structure, it raises the flange of the vent helping to eliminate leaks (water runs downhill - most people know this but RV manufacturers do not), the holes are already there, you will not need to make a mess demolishing the existing panel.
Patching fiberglass is really very easy, especially so if it is on the roof so the appearance of the repair is less of a concern. Done right, the repair will be permanent, as strong as the original camper, and require no maintenance ever. Go to
West Systems and you will find all the information you need - instruction, videos, etc. The materials are available at any West Marine store (curiously West Marine and West Systems are not related). I would use a couple layers of 6 oz cloth for this or the equivalent. The reason to use epoxy is that the secondary bond of epoxy is much better than the polyester the camper was made from. When you are done, paint the surface white to protect the epoxy from UV.
Bigfoot 10.4E, 2015 F350 6.7L DRW 2WD, Autoflex Ultra Air Ride rear suspension, Hellwig Bigwig sway bars front and rear