A post at AUGI asked about a roof condition that followed a curved wall. They wanted the roof to use a 1/12 pitch (1 inch rise per 12 inches of run for metric and slope in degrees folks). This is easy to do by specifying one segment of the roof as Defining Slope. This is the result.
Notice that the edge at the far left in the elevation is sloping? This is the sketch view using a slope arrow but it could have been done by assigning the Defines Slope parameter to the side sketch line segment too.
It was easy except they want the roof edge at the start to be parallel to the ground AND the roof edge at the end to be parallel too. Using this technique creates a roof object that represents a flat plate roof (imagine building it on the ground first, flat) structure that is lifted into place and the far end lifted up to create the pitch.
To create a roof that provides the parallel conditions at both ends we can use the Shape Editing tools instead. This will let us specify the elevation at each point of the roof. This also means that we are creating a warping roof surface. The rafters will each have a unique slope/pitch. Here's the result.
This is the sketch view of the roof using the Shape Editing tools and specifying a four (4) offset at the far left end.
Two approaches with different results. It all comes down to the desired result.