Roaches can be easily poisoned with boric acid. Folks used to mix it with a little corn meal and put it in their cupboards. Sometimes they would just scatter it around. Roaches are amazing creatures. They are immune to radiation that will kill almost anything and have been here since before the dinosaurs. Boric acid is much safer than standard bug poisons. In fact, boric acid is sometimes used as an eye wash (very dilute, of course).