How to get rid of cockroaches using natural products?
I have had great luck with boric acid based products for ants and roaches and just about any bug.  It's inexpensive, effective, and relatively safe.  It's easy to dust in the cracks and crevasses and gaps and spaces where they hide.  

Diatomaceous earth is another alternative that I have heard is just as safe and effective, but boric acid has worked so well I haven't bothered to try it.