Yes and no. As I have stated before, there are many things that will kill a roach, the most common example being a shoe. Smashing a cockroach with a shoe is generally 100% effective and is very cost-effective. However, ridding your home of a cockroach infestation with your shoe is an exercise in futility. I would apply this same concept to killing roaches with dawn soap. Cockroaches will eat soap, so it is not toxic to them. However, if you cover them sufficiently with a soapy solution, it will disrupt their ability to breathe through their spiracles and they will suffocate. So yes, Dawn soap will kill a roach when used correctly and accurately. However, it won’t repel or be passed on from roach to roach the way current pesticides will.