The most effective cockroach trap is an open glass container (jam or jelly jar), or anything like it that might be even larger, that has a couple of fingers of beer in the bottom and vegetable or olive oil smeared around the inside rim. The cockroaches are drawn to the smell of hops and barley and drown in the beer when they can't climb out. This will actually rid an area of cockroaches over a short time, and it works on American and German cockroaches just as well - which is handy because they're the two commonest pest cockroaches we have here in Australia,; the native cockroaches are plentiful and more numerous in diversity than anywhere else in he world (including the world's largest cockroach that some people keep for pets) but they're smart enough to prefer rainforests to residentiel homes.
We don't have a problem with cockroaches, but, we don't use chemicals and now we have a problem with flies since we changed doors and doorframes and had to pull down our old fly barrier (dangling barriers that we can't name and are trying to find replacements for). I found your site while hunting for "insect barriers". I've seen some very nice beaded ones over the years, one particularly nice crystal version and a Lebanese one made from polished wooden beads. But do you think I can even work out what the hell you call such a thing? No way! could it be something like a dangle-barrier, or, is there a Danglemaster Series of insect befuddlers? I'll soldier-on looking around for these unmentionable doohickeys and see what I can find... Wish me luck...
