Cockroaches are a high risk pest to have in your home as these dirty insects carry a range of serious illness such as dysentery, salmonella, and gastro-enteritis and typhoid. Although cockroaches are large in some parts of the world, the ones in your house are usually small. The problem is they generally hide during the day, and therefore if you cant find any of the insects in your place, it doesnt mean they are not there.
Eliminate sources of food and water. Keep food containers sealed and dont leave dirty dishes overnight. Remove trash from your kitchen and place it inside containers with tight-fitting lids. Clean your kitchen and bathroom regularly as these two areas often provide both water and food for cockroaches to survive and thus they are generally the favorite place for cockroaches to establish a base.
Cockroaches can live a long time without food (approximately a month!) but they cant survive that long without water. Avoid leaving standing water out anywhere. Repair any water leaks and dry out your sinks, the shower and tubs after use. Some people pour also bleach down the drains. You can also run the bathroom fan after or during showers so that excessive humidity in your bathroom can be reduced, as well as the air inside the rest of your house.
You can use boric acid as long as it is applied properly. Boric acid has always been an effective cockroach deterrent and its toxicity is low for humans but deadly to cockroaches. Other good options are to use cockroach baits, cockroach traps or roach spray (you can buy one of these from any grocery store). But again, if you have pets and kids at home then you should try non-toxic methods before going the chemical route.