Cockroaches come into your home through cracks and holes that may be in your walls and floors.
The cockroaches come in looking for food and if they find food they decide to stay in your home and then multiply.
To get rid of cockroaches in your house make sure you put any dishes up and cover anything you don't want contaminated and then get some fogger for your home to set off.
The fogger or bug bomber will release throughout your home and kill off the cockroaches.
If that doesn't work you'll need to get an exterminator into your house to kill off the cockroaches for good and they can then put a barrier around your home and find out where the cockroaches are coming in.
To prevent cockroaches in your home make sure you keep your house clean do not leave food lying around, especially in the kitchen and keep your kitchen counter clean and free of any food scraps.