Hello. Thanks for your question. The roof on this house slopes away from the center to a custom trough shaped into the EPDM roof itself that leads to an outlet on the back side. The rafters actually run the "wrong" way, allowing the shape of the trough across the slope like a colonial pole gutter, but hidden below the roof surface. The outlets were custom formed from aluminum coil stock flashed into the EPDM and include a "scupper" if the 4" pvc downspout ever clogged.
Good luck with your project!
Paul