×What I actually did do right after starting the room was kill almost every queen in the bottom 5/6 of the room before the first spawn, except for a few queens still positioned in the SE corner of the room.
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×As mentioned, after the spawn I retreated back into the entrance square to deal with the roaches that did spawn.
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×After this it was just a matter of killing the remaining bottom roach queens with my mimics while the northern queens took care of themselves. The last roaches caught north of the Halph space I took out myself, with quite a few turns to spare before Halph would blow up.