Cockroaches are the most common household pest , especially in apartments. Your apartment could be as clean as a whistle and you could still have German Cockroaches. The reason that you could still have cockroaches is because the people in the unit on the side,or below, or above you is a pig. So in that case there problems become your problems. There are many ways to treat for cockroaches, you can use a spray, something like raid, or you could use a bug bomb, or you could try home remedies. But the best way to treat for cockroaches is to use a bait where they would eat the bait and take it back and share with the other cockroaches.