The present invention provides a locking device for containers, such as waste containers. The locking device comprises a rolling member. When the locking device is in its upright position, the rolling member blocks the locking device from being able to rotate to an open position. When the locking device is tilted, the rolling member rolls to its release position which allows the locking device to rotate to the open position. The locking device also include a manual release mechanism for a user to manually place the rolling member into the release position, so that he/she can manually open the locking device when it is in the upright position.