Even if you deprive cockroaches of food, they can survive for months without eating. However, they die in 15 days if they do not get water. If you are not using any pesticide, it can take 10-15 days to get rid of cockroaches if you ensure they do not get any water inside your home. Even with a pesticide, it can take anywhere between 7-10 days to kill all cockroaches inside your home.