best layout for fallout shelter survival mode

I'm getting a little frustrated having to revive tens of dwellers twice a day because I looked away too long. One, single-room infestation, turns into five rooms with 90 roaches swarming everything that moves - all because I didn't catch it in time, and my armed, 5-stat, level 50 dwellers couldn't hang.

Now - this is all fine and dandy if you're constantly watching your vault and hitting people with stimpacks as they dwindle, but letting the game run at work and glancing down at my phone every few minutes, this can become a serious problem. Handy assisting them, to an infestation of five roaches. I just watched five of six dwellers die, with a Mr. NOW, with a vault at 200 dwellers, everyone equipped with a gun ( almost entirely sawed-off shotguns or better ), and a large number of level fifty dwellers - the incidents are becoming downright absurd. At that point in the game, I had probably half of my dwellers equipped with weapons, and most of them were somewhere just shy of level twenty. Early on in Fallout Shelter, I had the occasional incident from rushing, or just at random - and nine times out of ten I'd handle it without much of a problem.

Best layout for fallout shelter survival mode