Judy,
I have heard that you can use boric acid (it's a white powder you can get at the pharmacy). You can get an empty squirt bottle like a ketchup server (plastic bottle with the pointed spout that you squeeze) you can spray it into all the cracks and crevices, where Gizmo can't reach, and it is supposed to kill roaches. I have personally never tried it, but it couldn't hurt to check it out.
Hope this helps.
Here's a link I found:
http://www.mouthstick.net/tipsbits/boric.htm