When using the protractor tool sketchup s measurements box understands angles expressed as ratios as well as those expressed in degrees.
Sketch up slope roof.
An l shaped building in this.
Easily creates roofs with various parameters in sketchup plugin name.
How to create a uniform sloped roof in sketchup.
Typing 6 12 yields a slope of 6 in 12.
If you are creating a building that you that has odd dimensions that you want a uniform slope on read this article to learn how.
Create an odd shaped building.