Roof intersection

[elCid72]

Imagine an L-shaped house, each part having a simple gable roof, same roof pitch, same plate height. Each leg of the house is a different width, so the ridges do not meet ... the two roof planes of the leg die into the planes of the main roof. If I haven't confused you, here's the question.

What is the best way to adjust the length of the lower ridge so it ends right where it intersects the other plane? Right now I make a small adjustment in plan view, then look at an elevation, then go back and adjust, etc. There has to be a right way.