There are three factors that most affect the strength of low pitch trusses: pitch, span and wind speed.
Combine these three at their most extreme, i.e. low pitch, large span and high wind speeds, and this is where you’ll find a truss ‘working’ the hardest. I design trusses for many roofs around NZ that have these characteristics, your typical 5 degree longrun roof spanning over the lounge & dining rooms.