Last time I was in a student dorm in Saint Petersburg (3 years ago), cockroaches were in great abundance. However, in any remotely hygienic environment I haven't seen them ever in my life.
I suspect, this is mostly due to usage of powerful chemicals.
Now that I've googled a bit more, I've found some hilarious versions:
* Cockroaches are preparing for war, and they need soldiers
* Cockroaches are actually scouts for some alien civilization, and they already know enough
Logic, we love you.