Whether you build your own trusses or order them from the lumberyard, building a roof with trusses is much easier than framing a roof one rafter at a time. as a general rule when learning how to build a shed roof, you�ll need one truss every 2 ft. if you build your own, the cost will be about half this amount.. To speed up the assembly process, build all the trusses on the shed floor before erecting the walls. start by cutting all the rafters to length with a 40
