The room is not nearly as bad as it looks. It's pretty linear actually. Try experimenting around a bit with the first few obstacles the stallwart has to pass.
Answer to your question
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× I'm not sure which roach you are referring to, but I had the stallwart kill everything except for the stuff behind the yellow doors at (29,7) (29,9) and (29,11) and the Aumtilch at the very end (1,27). I let the briar deal with those. I suspect you're talking about the roach at 33,5 and just typoed. if so, more detailed hints below.
Possible hints if you meant (33,5).
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×Take care in deciding which direction to go when you get to (20,22)
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×I continued North (hit the pp at (17,4) - (20,4) to close off the other path.) and then cleared out the monsters at (33,5) (29,4) and (31,4) (note the pp at (18,2)-(19,2) will open up this group but toggles the other set of doors. You probably want to close them back up for the time being.
Hope this helps!
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Links to neat forum tools that I always have trouble finding:
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