You have to figure out where they enter the living space and may want to follow roaches through their trails to see where that might lead you. It is also important to make sure that you cannot close all holes and cracks because many roaches travel through vents and drains and in this case you will surely need an exterminator to help you fix the problem because otherwise this will be problematic.
You can try the manifold methods of killing roaches at home such as making roach food, using bait, traps, using water jars, applying liquid concentrates, getting professional pesticides and so on. Doing it on your own may prove much longer to do unless you hire specialists. You can also make a mistake and someone in the household can suffer if you are using poison. So it is always best to stay on the safe side and choose professional services for all these matters. In the future you can make sure the infestation doesn’t happen again by keeping the kitchen clean, putting food away in containers or tightly closed cabinets, emptying trash on a regular basis, fix leaks and dripping faucets, placing naphthalene in corners that will repel roaches.