To figure it out, you might draw it? Not sure what would be the "side" elevation in your case. You're right about the pitch. Use the protractor along the eave line, type 4:12, and make an angled guideline. Draw or pull the ridge line up to the guideline. Alternately you can figure how high the ridge would be by multiplication. If the building is 20' wide, then the ridge is 40" higher than the eave, (assuming it's a typical gable or hip roof)