Start off by drawing a standard roof using roof by footprint method. After you have completed the roof shape you want, finish the sketch.
Now select the roof. Go to the "type selector" and scroll down to “Sloped Glazing”.
You can now add grids and mullions as with any standard curtain systems.
If you need to edit the shape or slope, you can select the curtain system and edit it like a roof.
None Rectangular Curtain Panel note:
It should be noted that in any "none rectangular curtain panel" in a curtain wall or curtain system; you can only use System Panels. Revit won’t allow you to use Curtain panel.rfa family files. However there is quite a lot of customisation with a system file, i.e. with material, location and thickness. If you panel is rectangular, then of course you can use a customised curtain panel.