I think I'm going to become mad with this challenge.
I can reach the bottom-right part with 5 roaches remaining and with 1 roach following me and my caber pointing S, but I can't find a way to push it back without killing it, there's not enough space with only 1 barrier down. I also tried playing in the top-right corner, but all I can manage is to get 3 roaches following me with my caber pointing NW (where I'd need N or NE to push some in the arrows).
Maybe there's a trick with the roaches before reaching the first checkpoint by toying with the order of roaches, getting the slowest one first and pushing it back to gain 1 turn when there's an empty space behind it, but that would be so annoying to manage (if only possible) that I really hope that isn't be the solution.
Until now I haven't had too much trouble with the other puzzles, but this one (well, including the challenge) is by far the one giving me the most trouble. Given the very few hints in this thread I must be missing something obvious... but what?
My sanity would be very grateful for any hint