While paint will reflect some of the solar radation. However with no attic and no insulation - it's still gonna be really hot.

Not sure what you mean by reflective paint but we use the elastomeric (Kool Seal) available at both big box choices on our 70's era house trailer roof, a weekend place.

A coat of Kool Seal, which is bright white, will last us about 5 years and makes a world of difference keeping the trailer cooler longer during the heated months. A huge difference.

My concern over your roof is sitting/puddling water that will make the Kool Seal raise up. Our roof has some pitch so water drains off nicely.

yes, my roof does have a slight pitch I'm told, doesn't pool... I think I'm going to go for it....

We have a flat roof. Builder used a coating that was a medium gray. If you click on the link you can see my neighbors have the same medium gray sealant.

We repainted/sealed the roof with a bright white. I can say there is a marked improvement. Peak heat of summer, our house starts getting uncomfortably hot at noon. With the gray we could make it til about 1:30 or 2:00 pm without AC. We can go an extra hour, hour and a half with the new coating. On cooler days, we can go all day with no AC.

As I say in my blog post, there is more to energy accume than just LRV; specifically TSR (Total Solar Reflectance). But LRV is still an awesome piece of data, consistent point of reference.

Here is a link that might be useful: My Roof Project

My roof is an asphalt shingle sloped roof in Houston, TX. I used an all in one Barn & Fence white latex paint on my roof. I chose that over the elastomeric because it breathes to prevent water from being trapped. Roof temperature dropped from 190 degrees to 110 degrees. We had 107 degrees outside the other day and inside we were so cool we didn't even notice because their was very little radiant heat.

I highly recommend going white!

It's being done as I write, so soon I will know.... I'm guessing it will help... next I need to deal with the single pane clear skylights, which one unit has 3 of them, and they are large.......