I am wondering how do they get in, are they really tiny roaches? I don't like the idea of roaches in a click-clack, little micro environments where germs etc can cause a problem quickly if left unchecked. roaches can be quite "germy" I believe?. I would also be worried at the prospect of the insect taking little nibbles at my snake.
I can't really suggest any ways on keeping them out without seeing your setup, you could paint a strip of "fluon" around the outside of the click-clack to stop bugs climbing in (herpshop sell it I think). Ultimately I would stop the roaches getting into your click-clack.