But you can't really tell if they feel pain by how they're built.If you're really drunk and high you can punch through a window and feel no pain because your concious self doesn't recognize it anymore even though pain signals are being transmited from your arm to your brain through your nervous system.You still don't feel any discomfort.If you light a flame near a cockroach it will probably have the tendancy to move away(just like shining a laser on a spider
).If they really feel displeasure/discomfort/pain or is their "system" just detecting "potential harmful agents" and it's "processor" commands it to move away to conserve itself unconciously you can't really tell.Can't really tell if they're concious or not or how much are they......they don't really have a solid definition of conciusness anyway, but when it comes to cockroaches it's probably on a very low level.