You'll find people use anything from "spit and a Kleenex" to products recommended by the manufacturer. That said:
Simple Green is a "citric based cleaner" that contains Sodium Citrate.
https://simplegreen.com/downloads/SD...oseCleaner.pdf
Citric based cleaners are not recommended by Alpha Systems and DICOR. They are the manufacturers of the majority of TPO roofs on our trailers.
If you wax your trailer, Dawn (blue) and hot water followed by rewaxing is a common means to wash the trailer AND the roof.
Others (me included) use Meguiars yellow automotive wash with wax. I follow with a coating of Aerospace 303 about a week following washing. That week gives the wax time to "outgas the distillates" so the Aerospace 303 will bond better. It's a matter of using a petroleum based (water insoluble) product and a water soluble product on the same surface.