Seriously, get a grip. A roach, or in this case a few, can be found anywhere. I remember stayinfg at the Pearl Beach in Bora Bora in and overwater hut. When I opened the desk drawer a large roach scurried off into the dark. The room and property were very clean, but we're talking about a creature that will survive WW III.
Joking aside I have probably spent around 600 nights in hotels over the last 5 years & have not come across any roaches. I am also a regular visitor to Japan. Man is always in close proximity to roaches, rats etc - that doesn't excuse it. You have every right to be peeved and seek as many benefits as you possibly can for this outrage.