diamond 138Diamond Lake Campground Location: 80 miles east of Roseburg on Hhway 138, then Forest Rd. 4795 (Diamond Lake Loop) for 2&fac12; miles. Elevation: 5,190 feet: Nearby Gateway Cities: Roseburg - 84 miles Klamath Falls - 86Oregon Route 138 is an Oregon state hhway that runs between the city of Elkton and a junction with U.S. Route 97 at Diamond Lake Junction. The hhway has several distinct stretches,