We spent last summer in ID, MT, ND and other spots around there. Went across ID and then all the way up the panhandle to Canada on Hwy 95. Then back on Hwy 2 across MT and down into ND. I can't say that any of the roads we were on in those states would be a problem. They actually maintain their roads unlike some other states which seem to vanish their road money somewhere other than in asphalt. Of course if you travel in mountain areas you will hit grades, you can't have one without the other. But in general you won't see anything like CO passes up there away from Yellowstone.
Other than last year we have criss crossed all those states including AZ, UT and WY tho not so much in WA and OR, that's for this summer.
