I used to live in a house hopelessly infested. My family is clean. We nuked, to no avail. Even if you don’t leave food behind, the fuckers will find things to eat. Examples of things the roaches ate in that house:

• my favorite boot soles (leather)
• cold porcelain souvenirs
• wax used to lubricate drawers
• rotting wood from the actual wall panels
• debris stuck in brushes (hair and tooth brushes)
• paper

You can’t win. They probably have plenty of food in the form of decomposing organic matter inside the walls. For example dead animals, mold, rotting wood or else. I’ve had some success sealing with OCD levels of precision every single possible gap in the floor, wardrobes, walls, you name it. But there is always this or that thing you can’t seal such as power point sockets or else.