Hopefully they can convince the small folk to get them some help, if they can catch their attention! Sam and Dean always keep an ear out to see if there’s anything going on in the small folk world. They hear and see everything.
For all houses, you’ll actually find that there is a lot of space that you can’t see into!
For instance, we need a place for the pipes for the plumbing to go through, and the electrical wires that run through for the lights/light switches and electrical outlets. These can’t exist in a vacuum. Also, buildings will have space under the floors, as well. No matter how sturdy a house is built, you’ll find that mice and other rodents will always find a place to live, and this is the kind of space that the small folk use for their homes.
If there ever was a solidly built house, you wouldn’t find small folk living there, but that is definitely an out-of-the-norm situation.
Mostly, they just take efforts to keep the bugs out of their own supplies. Cockroaches wouldn’t bother them much, but if the population of cockroaches grows too large, they’ll have to make efforts to reduce it so the humans don’t call pest control. Everyone would be at risk if that happened. Out in the wild, the small folk would just ignore the cockroaches and the cockroaches would ignore them in turn. To each their own.