If you have the big water bugs that fly (wood roaches) then they just naturally make their way inside.
Now if you have the small wingless roaches (German roaches) then that is a sign of an infestation.
Order some of this from amazon and spray it around the outside perimeter of your house where walls meet ground to kill all wood roaches that enter.
If you have an German roaches then spray a very light amount around the inside of your house where walls meet the floor and in unused places like under the sink and behind furniture.
Also if you have ants it’ll take care of them too.
One package has lasted almost 2 years here and I spray about 1-2 times a month outside.
Roaches can be dealt with, but depending on location, they may have a habit of coming back, requiring retreatments. But that's still okay.
Your typical roach lives outside, but will venture into homes typically at night to search for food and water sources. They're nocturnal, so if you turn on a light you'll see them scurry. Best thing to do is to remove sources of decomposing organic material (as much as possible) from around the outside of the home. A lot of owners neglect the area underneath their decks, clean that out if you have one. If someone has stacked firewood or cinder blocks or something along the side of the home, get that out. (Also get rid of sources of standing water, as they're conducive to other pests like termites and mosquitos)
Once reasonably cleaned out. Buy a 1-gallon hand sprayer, preferably with some brass handle, wand and nozzle. And get some insecticide; I use Demon WP and they're little water soluble packets. Throw one in the sprayer, fill it up with water, shake thoroughly, and pump the sprayer and go.
Spray along the outside of the property, where the house meets the ground. And along any awnings you feel comfortable with, but try to avoid the wind blowing back on you. Spray under any decks, etc.
Doing that should greatly help. We just bought a place that had a bad roach problem, with us seeing 3-4 a night before bed (and I can't imagine how many came out after we went to sleep). And I did what I described above and counted 20+ dead roaches outside the next day, and if I counted that many then there were definitely more dead that I couldn't find. I immediately saw a huge reduction in the number of roaches I'd see. I've re-treated with another gallon of spray a few weeks later and have almost completely eliminated the problem, knock on wood.
If you see the small roaches, those are most likely German Roaches, and they're actually harder to get rid of, but it's not impossible. German roaches often come in to homes with previously infested items, like moving boxes, old furniture, etc. These can be problematic if you have neighbors that live in filth, etc. German roaches tend to be a bigger problem because they repopulate so quickly, so general insecticides don't always do the trick.
Best thing for German roaches is a little gel bait, you can get it a lot of places, check one of these Generally you can put small dabs of it in the corners of the inside of kitchen cabinets and then forget about it. It will eventually take effect.
I spray it two to three times a year. Nothing stops them 100% though.