If you are thinking of take SR-139 from Fruita/Loma a little west of Grand Junction and you don't want mountain driving that is not the route for your.
The road itself is fine, full width. However a few miles (20 or so) north of I-70 you have a steep climb with sharp turns and the same going down the north side. We drove it in our 40' diesel pusher coming south. This is the reverse of your direction. Going up on the north side, because of the steep climb and very sharp turn we were in first gear and 10mph for a few hundred yards before getting up into 2nd gear. Coming down the south side we were again in 1st gear for a few hundred yards because of sharp turn and steep road.
BTW we also drove from Ouray to Durango, and didn't think it was particularly bad. Just steep and slow driving.
If you want to go to I-15, take US-6/191 north starting just west of Green River, UT to Price and on to Provo, UT. There is a bit of a climb and decent north of Price, but not nearly as bad as coming up from Cortez through Telluride, which I am assuming is your route from SW Colorado.
