Roof over area without walls

[dwafford]

I'm trying to create a boxed-in window in a gable peak.  I can create the box with a polyline solid, but I can't insert a window into the solid, nor will the roof generate over the polyline box.  How can I create a box in the gable peak, into which I can insert a window and over which I can generate a roof?  Thanks for any help.  I've attached a pic showing something similar to what I'm trying to create.

[dwafford]

Thanks.  I tried that, but CA refused to generate a roof over it with only attic walls.  I tried building matching walls on the 1st floor and making them invisible, but then CA generated a roof over the invisible 1st floor walls, but not over the attic walls.  It also created a little foundation under the invisible walls.

[Alaskan_Son]

Build a second floor.