There are some roads that big class A drivers (drivers of big class A's, not necessarily big drivers of class A's!) may well wish to avoid, but there are plenty that are perfectly suitable as well, including as has been said the highways to and from Alaska.
When I went last year, three of the places I liked the most were all at the ends of roads that I think a large class A might have trouble with, depending as much as anything on ground clearance and the driver's nerves: Eagle, Galbraith Lake campground on the Dalton Highway, and Kennicot/McCarthy. The latter is not that hard to get to as a day trip, though camping in the valley beside the river was enthralling (even though the campground severely lacks amenities). That being said, there are many other great things to see and do that don't require driving on horrible roads.