Sealing larger holes in roof

Wow. That seems like a lot of work for somethinng no one will ever see. I picked up a 1978 coach that someone removed a roof carrier from - 18 holes left. I got plastic hole plugs from Sears Hardware ( now out of business ). Cleaned up the holes perfectly round put a slight amount of urethane adheasive and snapped them in place,
The plugs also came in colors but I used white. I probably had about a hour in the whole project. If the holes are standard antenna holes they also make rubber antenna hole plugs used when removing 2-way radio antenna.
 
I have had a couple thoughts on this. I will have some holes on my roof to patch. The holes from the screws to roof rail, just a closed end blind rivet. The bolt holes from the cargo carrier might work with a large head rivet or just glue a patch on the inside and trim the panel adhesive flush with the roof.

The larger holes <1", I've considered a disc the size of the hole with an inside backer and panel adhesive to make a flush patch. Larger patches I'll just use panel adhesive and closed end blind rivets.
 
If it were me I'd find some good thick aluminum, cut out a patch 1" bigger on every side, bend it, shape it to the curve and pop rivet it down, then Dicor over the top of it. Never silicone.
It’s interesting that you recommend Dicor. Maybe I purchased the wrong Dicor sealant (lap sealant) but the stuff I bought doesn’t ever dry - remains gooey. I used it to stop leaks at the top edge of the windshield weatherstrip and it remains gooey. In fact, the front cap paint is peeling and it sticks to the sealant. It did stop a lot of roof leaks but it sure doesn’t seem like a long term solution.