log cabin roof framing

Hi: A real newbie here, I'm building a log cabin, walls are up but now a question on roof framing. The cabin is basically a 30ft. by 40ft. rectangle, front entrance is a 6 ft. bump out, because of the log construction this bump out wall is approx. 5 inches higher than the other walls. How do I frame in the valley rafters with the walls at uneven heights. Both main and entrance roofs are to be 11/12.
Thanks Gary