The first thing that you need to make sure is that the "Export room geometry" option is checked prior to exporting the Revit model to Navisworks 2012.
Then in the "Find Items" dialog accessible from the View tab of the ribbon under the Windows drop-down set the following line in your search:
- Category = Category
- Property = Name
- Condition = =
- Value = Rooms
This will find all Revit rooms in your Navisworks model where you can then save this as a search set for future use without ever having to update your selections.