Do you wash your roof?

I wash my fiberglass roof a couple times a year with Dawn dish soap.

We live in an agriculture area with a lot of dust and if you don't wash off the roof you get mud streaks down the side of the coach.

Not just you.
I wash the roof of my TT once in a while. Not as often as I was the body but I still do it.
Keeps the buildup of black spots and tree stuff etc from getting too out of hand.
And it's good to inspect things while I'm up there.