dust66:
If you are using the Roof Tool to create the ramp (which would be my suggestion), in the Roof Settings > Geometry and Positioning > Roof Pitch, there is a small triangle at the top right of the input box that allows you to choose the angle units, one of the options is degrees. This will create a ramp of that angle, or if you have already placed a Roof as a ramp, you can select the Roof to check its angle. This same pitch and units options can be found in the Info Box for the Roof Tool.
You should add a Signature to your Profile (click the Profile button near the top of this page) with your ArchiCAD version and operating system (see mine for an example) for more accurate help in this forum.
David