Murf2, You can usually tell a lot about the roof by the ceilings. If you have looked hard at the ceilings and did not see things like stains or mildew on or around it and or windows its probably not an issue. you can also crawl around the roof and look for cracks in the sealing material around the seams and vent areas. If you see big globs of sealant in a particular place, go back and search for weak spots and hidden signs of seal failures in the corresponding places on the ceiling. It's a real task to find that perfect Motor home and your doing it right, ask questions seek advice and have fun with it.