I have always (5 years now) cleaned the rubber roof on my trailer with Protect All's rubber roof cleaner and then applied Protect All's rubber roof sealer. You can buy the stuff in some WalMart stores.
Just Dawn dish soap. Alpha says no oil based cleaners on their rubber roofs.
Dawn is a good product and I have used it too. I believe the concern is with petroleum based products. Most EPDM rubber roof manufactures warn against using petroleum or citrus based products. FYI Murphy's Oil Soap is a vegetable based soap product.