mysql: select all items from table A if not exist in table B

I am having problem with selecting values from table a (id, room_name) where there are no corresponding events in table b (room_id, room_start, room_finish)

my query looks following

SELECT id, room_name FROM rooms 
WHERE NOT EXISTS 
(SELECT * FROM room_events 
    WHERE room_start BETWEEN '1294727400' AND '1294729200' 
          OR 
          room_finish BETWEEN '1294727400' AND '1294729200')

table a contains multiple rooms, table b contains room events I am getting no results in case there is any event for any of the rooms within the timestamps. I am expecting all rooms having NO events.