Although it has been a few years since anybody posted to this topic, I'd like to add my 2 cents nonetheless. First of all, that demo is horrible! In it, Beethro wastes a lot of time in the first part. He also comes very close to screwing up several times.
I managed to beat this room on my first try, and none of the roaches ever set foot on an arrow. However, I was able to accomplish that because, before actually attempting to beat the room, I figured out what all the orbs do and made a PNG of it. And I thought very carefully before making a move in a number of places. And when I got to the part with the 4 roaches, I made a replica of that area so I could test a plan for killing them (as it happened, the first thing I tried in the test room worked).
Despite that, I'd still say that either this room or 1 north is the hardest room on the level. It certainly took me longer that some of the rooms that took me multiple attempts to beat.
Anyway, the way I did the part with the 4 roaches was:
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Move mimic north of orb
Make mimic strike orb
Turn sword clockwise twice (so it faces west)
Go west, then southwest to kill 2 roaches
The other 2 can be killed with sword-turning instead of movement