Abstract: A roofing system that provides a safe, long lasting, leak-free and maintenance-free insulated roof for flat roof applications. More particularly, a sandwich panel comprises an inner foam core, a fiberglass skin fully encapsulating and surrounding the core, and a gel coating surrounding the skin. The panel has two substantially parallel surfaces and a peripheral edge having a step edge. A plurality of panels having two different shapes and relative dimensions are alternately secured to purlins to form the roofing system so that half of the panels can be easily removed without affecting the rest of the roof.