A multi-layer roofing membrane is provided including a top sheet including a co-extruded cap and inner layer and a bottom sheet. The use of a co-extrusion die allows for multi-layer sheets that reduce the need for expensive fillers in all but a cap layer of the membrane. A scrim reinforcement layer is optionally embedded in the membrane. When installed on a roof substrate, the membrane can be sealed by heat welding the seams of the membrane sheets or by other means.