It's probably TPO since Fundfinders were intended to be lightweight and TPO is significantly lighter than EPDM.
But to be sure you can remove a roof vent shroud on the INSIDE of your trailer. The roofing membrane has been cut and folded back against the vent opening. If the roofing membrane is black with a "colored surface" then it is EPDM. If there is a felt backing that obscures the base membrane, it's TPO.
2011 Chevy Silverado Crew Cab 4X4
2009 210 WBS