Well the problem stems from a feature that was introduced in Revit 7 that allowed adjoining sides of a footprint roof to have different eaves heights. A side effect of this new functionality was that roofs may not generate the shape you want.
Here's our floor plan.
Nothing particularly special there.
Here's the sketch of the proposed footprint roof.
And here's the roof generated from that sketch ( in Revit Building 8.1 )
This is what we were hoping to get.
Using this sketch as a base, we can generate the roof that we want.
First delete the old incorrect roof.
Now we need to analyze the geometry of the proposed roof. Looking at it, it would seem possible to create it as two pieces of roof.
We construct the first piece using pick walls and slope lines and then pick the sketch lines for the valleys, hips and ridges.
The first part of the roof now looks like this.
Now, we'll make the second part the same way.
It's taken more effort than a " normal " footprint sketch, but in the end ...
On the roof, it's peaceful as can be
And there the world below can't bother me
Let me tell you now.