Figure out how much time you've spent dealing with the issue and how much longer it's going to take. Multiply that out by some kind of reasonable salary-style figure (like $50/hr). This is especially imporant if you've done anything like taking time off of work to deal with this. Get an exterminator to come in, add in whatever it costs to stay in a nice hotel for a few nights while the house is getting fumigated (Gotta be safe, after all!), the cost of the exterminator for a couple of visits, etc. Organize all the costs nicely, lay it out in simple terms and send it to their public relations department and see what they do. Be sure to include all your pictures. If you still have it, try to get some pictures that clearly say "Cox" on it with a roach (dead or alive) somewhere.
Give them a certain amount of time to pay your "bill" and notify them that if they do not do so you'll be filing a complain with the public health department, the BBB and notifying local and national news agencies. I can just see a site like Fark loving this story...
Just don't mess around, get it done while it's still on their minds.
- G