I've created a Death and Whipping boy room to mitigate events and kill off unwanted dwellers.
Events scale with the upgrade state and size of the room, so, if you create a basic small room that you can Spam the Rush on, to make failure events happen on purpose, plus put dwellers inside the room with decent armor and weapons, you can create events on purpose, small events that only last a few seconds, but events none the less which can keep other random events from happening.
Creating events on purpose by spamming Rush on one room until it's failed Rush a few times, a small basic room where the event only lasts a few seconds with two well armed and outfitted dwellers, keeps random events from happening.
Want deathclaws to stop showing up every time you open the door?
Spam Rush on the basic room until it fails a few times (with 2 dwellers to keep the event only a couple seconds) before opening the vault door and also a little bit after it's closed.
Too many dwellers?
You can use the same room to kill unwanted dwellers.
Strip the ones you don't want down to vault suit with no weapon, and spam Rush that basic small room you've made until it fails and keep doing Rush until they die.
You might want to have another room close to this room, so, when you kill the dwellers inside it, you have other dwellers waiting to put out the fire, kill roaches, or stop molerats from spreading to other rooms.
Having a room like this is also handy for those objectives like "Stop # fires", "Stop # events", whatever. Spam the Rush on the room you've created just for that purpose, and heal the two dwellers, over and over and over until you've stopped however many fires, or events are required.
Don't upgrade the room and keep the room small.
If you upgrade the room or make it bigger the events will scale to be stronger and longer.
Keep the room basic and small and eachevent only lasts a few seconds if you've put two leveled dwellers will good weapons and outfits. Since events only last a few seconds, you can do Rush over and over and fail over and over many times in just a very short time.
Also, if the room is kept isolated and not next to any other rooms, like two levels down with dirt all around it, molerats, fire, and rad roaches won't spread because theres no other rooms touching it.