Rooms cannot be deleted until every assignment for that room, from any year, term, class, and activity is removed. There is no easy way to do this in bulk, and there is not one report that will summarize each room assignment from every possible place.
So, if a school remodels a building--or in our case, moves the lower school to the old upper school building AND remodels--it becomes a huge job to delete old rooms.
Ideally, we should be able to delete rooms that are not currently in use (archiving past years would be good).
Short of that, a bulk way to remove the assignments, and possibly a report by room that shows all assignments to it (from any year and any activity) should be available to speed up the process.