S t u a r t,
The type of roof you are modeling is really easy using
the mesh tool. It has four nodes, no ridges, the edges
can be arcs. and the two up hill nodes need to be assigned
a higher elevation than the lower two nodes.
And, of course, the SEO bit to slope the underside.
To have a mesh radial roof have shingles you would have to
draw the shingles in a radial pattern and make a symbol fill
out of the drawing and apply it to the mesh material.
A pain, granted.
Peter Devlin