We had a horrible cockroach problem in a condo that we rented for a month in the tropics.
The thing that worked the best and longest was this poison gel that looked like peanut butter.
I put a tiny dab everywhere that a cockroach might like to walk or hide like along the baseboards.
They would take the poison back to their nest and feed it to the other roaches. Within a few days the problem was 99% contained.
It looked like this product.