If you are using USFS roads, go to any office of the National Forest you are in and get a copy of the Motor Vehicle Use Map (MVUM). These are free, so no excuse to not have them in the rig, and for each Forest you visit. This will show the road system that is open for motorized travel.
It is up to the user to know where they are and if the route they are on is open for use. They are not required to post routes as open, as the policy now is "closed unless posted opn", and the map serves as the posting of open routes. They are not even required to put road number signs up, though most do/are.
Most Forests have completed the first phase of their Travel Management Planning, but the second phase is starting now, and that will close way more roads to get down to their "sustainable" level with the budgets they have for upkeep.