I think the complicated part here is that you have to define which sides are the ones that have the steep angles.
I´ve acomplished gable rooftops so far by generating a “normal” roof first, then taking the very upper curve of this roof, extend it to infinity, intersect it with a extruded surface of the base-surface and then combine the edge vertices with this intersection point. Might be a bit complicated but it works very well. In this case I never have to set the lines of the steep angles manually…
