Curved roof with a slope and two different curves

[ChrisKlms]

Hello, beginner here,
I have a Ruled Shell defined by two arcs at different heights. The shell is flat/diagonal but I need it to follow two curved profiles which are arcs with different central points (low at the inner edge, curving up and over to a higher outer edge, see attached plan with center of curves). See screenshot attached. The red line shows the desired profile in section. I can't seem to modify this "section plan" as it follows my curve. I tried many other tools like slab, roof, wall but nothing seems to work and shell is the closest I got. I am not very familiar with the tool, is it possible to obtain my desired profile ? It has to be a single simple shape as I use it for rendering etc. so It has to be easy to modify, I'm sure it's possible as it's a very simple shape but I spent the afternoon trying to make it work. 

Thank you for any help

[cuba]

So you want a roof with varying curvature, where the eaves line is consistent (horizontal) everywhere, and the ridge line is also consistent (horizontal) everywhere. The roof does not lie in a single plane, but each rafter has a different pitch.

[runxel]

First draw your shell with this method in the floor plan

Then rotate it in 3D 90° so its axis is parrallel to the Z-axis.

Back in 2D the trick now is to use the menu command "define shell contour". You can then draw the portion of the shell that you want to keep.