Is it possible to show the two end walls being rounded? - not too worried about showing actual roof, just the walls.

• BUT you get pretty close if you split the wall into several elements and adjust the wall heights along a curve. Depending on how patient you are, how many wall elements you use, the result should look ok.
• OR you could stick a separate gable on top of your wall (made from some curved object stretched to fit).
• OR, you could use an opening across the top of the roof and specify a cut-out with the SVG arc command (you would need the furniture library editor and an invisible window).