Down here in Florida, roaches are pretty common. It's not always a matter of cleanliness; our houses are cozy and secure, who wouldn't want to crawl in and live it up?
I had one case with german cockroaches in the kitchen. However, the family lived in an apartment, and although they kept the place spotless, they couldn't control what neighbors did. The exterminator would spray one apartment, they'd scurry to the next, and so on and so forth. Also, these kinds of roaches were notoriously resistant to pesticides. They weren't in the patient's room, and all his supplies were kept safely sealed in tupperware, so it wasn't an issue.
Ugh, I did have another house that was overcrowded, disgusting and the OUTSIDE PORCH had been hastily constructed into a separate bedroom. The place reeked of body odor and wet dog, and there were roaches all over the kitchen, which was connected to the kid's room. The mom repeatedly would yell from other parts of the house, "These nurses will report me and my baby will be taken away." Mind you, she had 24-hour nursing and never really came in to interact with her son...
Oh man, the things no one tells you about in nursing school