Roomba is a set of tasks which periodically delete questions based on specified criteria. There are 5 Roomba tasks: 1 runs daily which deletes questions closed for > 9 days when they also meet other criteria. 4 tasks run weekly to delete questions which are either > 30 days or > 365 days old and which also meet other criteria. The criteria can be found at: http://<Stack Exchange domain>/help/roomba : e.g. http://stackoverflow.com/help/roomba

For more information, see the description of Roomba at: