×I think I have to carve a long enough path from the trapdoor area that the roach will want to go around the block, and then at the right moment I'd kill the brain and thus cause the roach to fall into the snake enclosure. But I can't find the proper shape that's long enough, leaves a way in and out, and all of this with the roach on top of me.

×That's right.

×All you really need is a horizontal line of dropped trapdoors with the roach on the opposite side from you.

×And an escape route. Partial demo attached.