What model year is your RV? At around 10 years old, it might be better to coat a roof that is in 'good' condition, or fair condition, rather than waiting like I did until it was 14 years old and in such poor condition that all the white stuff washed away when I was cleaning it and getting ready to coat it.
Try this stuff. It is as easy to apply as paint on a wall. A lot thicker, and does not run like paint. It took about 8 gallons to coat my 30' long RV.
http://www.epdmcoatings.com/videos_play.php?vid=25Good luck,
Fred.