This is very simple

You have to modify/manipulate (manage) three things and this is called Integrated Pest Management (IPM)

1) the environment

2) the organism itself

3) Its propagules(reproductive means)

Environment,

Cockroaches hide in hidden places, small openings and crevices in the house and it is in these same areas that their eggs are laid or attached to, they love thrash, spilled sewage, left overs etc.
A major feature why they survive easily is their ability to feed on anything (especially the adults). they eat so many stuffs.
modifying the environment means no access to easy food. keep food stuffs in air tight containers, dispose unwanted ones properly. The ability to feed on anything is exhibited by the adults while the small nymphs require jelly/slurry/liquid foods.
Block possible hiding places and crevices,

The organism itselt

Cockroaches are very successful because of their totality, they can feed on any thing, live anywhere, strog body covering, produce many young ones etc,
this then explains why multiple approaches must be used to control them.
you must make use of Chemical control as one of your methods and the purpose of this is to attack directly the active and living form of the organism and not its reproductive structures(the egg)

you must however note that some of this fully developed ones go into hiding during periods of lethal chemical concentration, and then re emerge when the chemical level goes down. and as such so many of them escape these so called chemicals.
However, blocking these holes and crevices before spraying or spraying them properly and then blocking them is very important.

Reproductive means(Egg)

it will however surprise you that after few weeks small Cockroaches will start springing out and in few months the Adult population is replenished.

The Cockroach egg has been designed with a hard covering to protect its content, and infact survive many chemical attacks, therefore, these eggs hatch, grow through the developmental stages and become Mr Cockroach again.

The good news is: if the first two steps were properly followed then the next step and not the last is to repeat the the chemical spraying after two weeks to kill those that were hatched two weeks after the first spraying and another spraying will be required after another two weeks to kill those that were laid just before the first spraying as it takes 30days for the egg to hatch, you might aswell consider another spraying after few weeks, as you never can tell

And finally make sure none find its way into your house again as just one with a fertile egg is enough

Live and let the roaches live.

Thanks op. That was very helpful. Keeping the kitchen neat n tidy also helps 2 prevent them.

otobrisesarah: Thanks op. That was very helpful. Keeping the kitchen neat n tidy also helps 2 prevent them.

uwc