We currently have a Sportsmobile 2WD and are kicking around the idea of getting a 4WD vehicle. Not sure yet whether we want to go with another Sportsmobile or with a truck camper. (We currently have a...
Almost all main forest roads in WA/OR have a high canopy to allow for fire trucks and logging trucks. Secondary roads can be lower and more narrow, but usually not by much.
As long as you have strong tires to deal with the large rocks that they rock the roads/gravel with, you should be fine.
You could always sample some of the roads you think you will travel and take a look.