Hey, I´m new to SketchUp and am struggling to create the roof of this house as a singular face due to it´s non-quadratic form. So I´m wondering, how I could create it as one face, which would make the process of thickening the roof a lot easier.
Thanks in advance 
You should post your model. Or a screen shot or image of what you want to make…
As @bmike wrote, share the file so we can see exactly what you have modeled so far.
Keep in mind that the edges of a face must lie in one plane. A face cannot be created if the edges are not in the same plane.
I’m not sure what you mean by “non-quadratic form”. That says what it is not, but leaves infinite possibilities for what it is.
In any case, faces in SketchUp are planar polygons; quadratics of any sort are not supported. Curved surfaces are built as a collection of polygons with the edges between them softened and smoothed.
Oh, yeah, I forgot to add the screenshot 
I would make the walls a group / component and then make the roof a group / component with thickness, and then rotate it into place…
If you don’t know what I’m talking about (groups, components) - start here:
Find the product you are using and start with the basics.
Sharing the actual SketchUp file would be more useful than a screenshot. If you can’t delete those diagonal edges across the roof surface and keep the face, the bounding edges are not in the same plane.
