Repair leaky pipes and faucets. Try to reduce the amount of standing water in your house and don't leave out soap bars. Roaches are attracted to both. If these preventative measures fail, try using a least toxic chemical control - use a sticky trap or put a light dusting of boric acid behind and under the fridge, stove, and duct work and in or along cracks and crevices. Be sure that your kids don't have access to these areas, as boric acid can be harmful to children and should be kept out of their reach.
Ants Locate the place of entry and squeeze some lemon juice on it.
Leave the peel at the entrance. Ants will also be repelled by chalk, talcum powder, and coffee grounds. As with cockroaches, plugging cracks, holes, and water leaks is a good preventative measure. Flies Sunny open windows are a fly's entry way to your house. So close your windows before it gets sunny.