best way to clean the roof?

Having spent the last several hours up on a ladder mopping all the dirt off our 2720 (but it had a lot of old dirt and a pile of undiscovered hail dents!), I'm wondering what the best way to clean the roof is? Can I just use a hose? Can I get up on it and scrub? I had read somewhere that a pressure hose was a bad idea but is a regular hose ok? Oklahoma gets pretty dusty and it is all red dirt, which makes for a dirty camper pretty quickly. I suspect the dealer cleaned this but this is just accumulated dirt from the last month or two on the lot.

-Amy
2004 2720