Form mesh and adjust points on edge to correct z height.
Use the goodie add on convert mesh to roof and that's it!
Remove original mesh, check that roof at right height.
OK?
Chris Phillips
(User since 1989 on more systems and versions than I care to count!)
Or, if you know the exact heights of those points you can create the individually Roof planes in the 3D Window, where you can define a Roof by specifying 3 points in space.
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