I've just redone the roof seams on my LY - after removing all the sealants used, I resealed the seams with lap sealant and then taped over the seams with Eternabond tape. I bought the tape from the factory (two 37-ft rolls) and it came with a lifetime warranty against failure (meaning leaks). Because I have to regularly go on the roof to clean the solar-electric panel mounted there, I would not want a rubber roof coating as it would not stand up to repeated access.
My '94 LY has one skylight over the shower, which I had the local AS dealer order in for me about 3 years ago. The other "domes" are vents - the one near the dinette is a Fantastic Fan, and FYI this has a lifetime warranty from the factory, so you can call them about it. They have replaced parts of mine over the past few years, and at the International in Bozeman, the factory rep redid mine.
The vent over the toilet is simply a regular vent, but it has a small exhaust fan and power opening and closing. This is a "normal" everyday RV replacement item - as well as the Maxihood over it to prevent rain from getting in.
1987 Excella 32-foot
1999 Dodge Ram 2500HD Diesel