Happi,
Welcome to the forum!
Please ask your dealer "why" it needs to be "sealed"?
If the trailer has an aluminum roof, it does not need to be sealed.
If it has a steel roof, is it rusty?
If so, after cleaning, the sealer can help prevent further rusting.
If it isn't rusty, there is no need for "sealer".
If the roof leaks (you said it doesn't) then the roof needs to be repaired, not sealed.
If you want to try to make it slightly cooler inside, you can use a "sealer" to help reflect sun/heat back away from your roof.
It is very common for people in the RV/mobile industry to recommend/speak of "coating" roofs (quite profitable).
What they should be telling you/know about, is that each year you should carefully inspect each seam/joint/overlap that requires a sealant to remain waterproof.
Areas such as windows, doors, roof vents, siding overlaps, etc. all rely on a sealant, usually roll putty to prevent water intrusion.
Slopping "sealer" on a roof every year adds a lot of weight, costs a lot, and does nothing to prevent leaks should the roll putty fail.
What it can do however, is allow water to seep under it (between a failed bond between sealer and roof, and allow water to work away at entering the structure un noticed until major damage is done.
Imagine water getting in at one end of the roof, but showing up as a ceiling stain at the other.
How will you ever find the entry point?
Learning to inspect your roof every year is not hard, and will prevent damage that other owners chase for years by applying more "sealer" on their roofs.
Rob (who isn't a fan of sealer for preventing roof leaks)
Waiting for "someday" will leave you on your deathbed wondering why you didn't just rearrange your priorities and enjoy the time you had, instead of waiting for a "better" time to come along...
Welcome to the playground Leigh.
The roof is fine now, so I'll leave it be.
