Cockroaches, what can you say except they're nasty. If you find that you have cockroaches the first thing to do is make sure you clean well, keeping all food in sealed containers. Don't leave dirty dishes in the sink and take out the trash. After you have cleaned thoroughly, try sprinkling Borax inside all of your cupboards, except where you store food. Brush it all over the bottom of the cupboards and be sure to get the Borax into all of the cracks. Where you store your food you can leave an open container of Borax to keep the cockroaches out. Boric acid will take some time to kill the cockroaches, but it and cleaning well are your best defences. Also be sure not to step on cockroaches as you can get their eggs on your shoes, enabling them to spread.
