Hi Dan! Welcome to IRV2! We're sure glad you joined the gang!
Not knowing exactly what kind of roof you have it's hard to recommend something. The 4" wide Eternabond tape will stick to most anything if the surface is reasonably clean. You can use that to seal around skylights, vents, etc. For small openings like vent pipes, TV antenna, etc. I would use the Dicor 502LSW Self-leveling sealant. Hope this helps!
Good luck, happy trails, and God bless!
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Joe & Annette
Sometimes I sits and thinks, sometimes I just sits.....
2002 Monaco Windsor 40PBT, 2013 Honda CRV AWD