Sometimes called a ‘shed roof’, a skillion roof is similar to a flat roof, but uses a steeper pitch which allows for better drainange. skillion roofs offer lots of. Derek pater recently contacted us to do a review of his unique roofing protractor system. the tool simplifies many of the calculations that go into building a roof. Welcome to the next generation of building designs. allgal garages and the williams river steel group are proud to bring you the curved roof range..