I had that issue about 15 years ago when I purchased a house. It not only had german roaches (lol didnt know I was lucky enough to get foreign oneslol) but also kept hearing skittering in the chimney and the ceilings..
Well had the exterminator come, he went investigating and found that I had fleas, mice, roaches, and raccoons!!
Now I had just moved in (well the stuff was not even there yet thank goodness)
So he sprayed, baited, trapped, you name it he did it. Death toll in my "new" home was high. Now this was an old farmhouse in the middle of cornfields but when we looked at the place and had it inspected that was not on it nor did we see anything
.
I just waited till everything was dead for sure before me, hubby, kids and pets moved in. That meant an extra 2 weeks at a hotel and doggy motel. Talk about money!!
Well I can tell you that for the first month everything I had for food or purchased was put in the fridge or freezer where those buggers cannot get to. I was taking no chances!!
I wish you luck