For the rubber roof I use just plain old water. I have a soft bristle brush with a long handle. It attaches to a garden hose and water flows through the brush. This allows me to scrub away the grit and grime while the water rinses it away.
Once the roof is done, I rinse off the sides of the trailer and scrub the grit & grime with the brush. I will use soap (Simple Green in spray bottle) to get rid of black streaks and bugs. Rinse again to get rid of the loose stuff. Then I use Turtle Wax Zip Wash & Wax https://www.turtlewax.com. You spray it on and rinse. It dries and has a shine that looks like you spent all day waxing.