I can’t make faces here, but this is what I have to work with (two parallel 10/12 roofs joined to each other). I’m sure I’m doing something wrong, but I don’t know what it is!
Any ideas?
Thanks in advance!
Please upload the file as is. One can’t tell from such an image. A 3D model is needed.
Or conversely learn how to draw a rotated rectangle or a sloped one and use Su inference engine. I find that is what help is for 
More than likely the plum cut and angle are not in plane. For quick fix I would delete left geo, copy / move right over and up to the rake interface and go from there.
If you can’t make Faces, the Edges you have drawn for the boundaries aren’t co-planar. However, it is about impossible to tell from the figure exactly what is askew - can’t tell normal perspective effects from non-planar surfaces. That’s why it is always better to upload an example model.
The User controls the Axes
The Axes steer the Inference Engine
The Inference Engine steers the Tools
The User can lock Inference via Shift and Arrow keys
Search Results … Aidan Chopra Video Tutorials … #Roofs
https://www.youtube.com/user/aidanchopra/search?query=roofs
Axes
Inferencing
Inference Locking I
Inference Locking II
Accuracy
Tape Measure
Protractor