Consider them out and varnish 'em on a regular basis. In locations where heavy rain and/or snowfall is a recurrent function then you don't have to worry about water accumulating on you roof.
Nevertheless, when you have a flat roof all you need is a ladder, cleaning equipment and regular legs. https://njspmaca.in/2024/06/27/an-over-view-of-rubber-epdm-and-epdm-flat-roofs-3/