Get yourself a travel plan map from the forest service for that area, it will list what roads are open and what they are open too.

Most places I go the roads are posted as to what the allowed use is, if it says closed and nothing else then it is closed to all motorized traffic, but if there is another sign with little pictures of atv, motorcyle, bicicle, horse, hiker and they have open and closed stickers or open closed dates then you go by what the sign says.

Best to get the travel plan map and if you have questions call the forest service office for that forest.