I am sorry for this delayed reply to your gardening question as we are transitioning to a new Q&A system. I hope this reply is not too late to be of help.
It is very difficult to kill those large roaches outdoors since they love living in organic matter and mulches. There are many general purpose products at your local Home Depot which will make an initial kill (sevin dust is one such product) but the roaches will likely return fairly soon. You might try one of the bait stations that have growth regulars in them. However in the ourdoor environment these stations will not last long. Perhaps you can create a cover with a board to protect them from the elements.
Thanks for the question. Please stop in again soon!
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