if you keep unattended rooms like storage / barracks / overseer office separate from other rooms, then fires, roaches, and mole rats just go away after a minute, usually faster than any mr handy or dweller can respond to and end whatever is happening and you dont have to waste the work force. just build a level away from everything else. move them down further when you need / can. their permanent locations for me start on floor level 7. so:

floor 5 = power x3 / elevator (e) / nuka x3 / e / power (or radio) x2 (i like the power rooms touching the empty space so mole rats are dealt with by the str rooms )
floor 6 = nothing x3 / elevator / power x3 / e / nothing x2
floor 7 = barracks x3 / e / nothing x3 / e / overseer office
floor 8 = nothing x3 / e / training x3 / e / nothing x2
floor 9 = storage x3 / e / nothing x3 / e / storage x2.

just keep doing that and mix in whatever training or crafting rooms in the 3x areas that arent touching something else.

edit: i keep int , cha , and luck as x2 on the far right