Freeze they keys to your cuffs, chastity belt, and lockable onsie in a plastic bottle of water (or ice cubes). The next time your roommate leaves, you must put in your butt plug, and put on your chastity belt, cuffs, and onsie. And flip a coin, if it is heads you must also wear a diaper, tails must remain how you are. As soon as everything is in order, you may take out the frozen keys. Hope they melt fast! :D

Any chance to get a wedgie related one??

Freeze the key to a padlock. Then give yourself a hard wedgie. Loop a belt through the wedgie and around your shoulders so it’s secured in place. Then padlock the belt buckle so you can’t undo the belt without opening the padlock.

Freeze the key to a padlock, and then lock yourself into a bra connection wedgie.

Lock yourself in a super tight wedgie. Hide the key in your least favorite food. You must eat through the food to get out of the wedgie.

Freeze the key to some handcuffs or other way of locking your hands together in an ice cube. Drink as much water as you can stand to and wait 1 hour. Cuff yourself to your bed in some way. You can't get up until you melt the ice cube

Tie the key to some handcuffs to a collar and put it on. Then cuff your hands behind your back through a pair of underwear so you are forced to pull it into a wedgie to reach the key