How big of a rig? US 550 is not for the faint of heart, but i would have no problems taking my 35 ft class A over it. My wife says she would be scared. Definitely not in the winter.
We had some concern about that route several years ago and so we drove it first in our car. We didn't see anything that we thought we could not handle in a 37' coach and towing. However, our plans changed (not because of the road) and we never actually traveled the road in the RV.
We drove 550 from Montrose to Durango with 40' fifthwheel. Beautiful ride. Depending on your skills at mountain driving, it's no problem. Lots of campers and 18 wheelers take it. If you don't like mountain driving I would suggest not taking it.