Answer: I don't know of any beetle that looks like a roach and feeds on crepe myrtle leaves. I assume you mean "leaves" when you say "destroying the inside of the trees". June beetles are brown and about 5/8 inch long and half that wide. They are foliage feeders. Their bodies are rounded, not flattened like a roach.
It may be that the insects you are seeing are roaches, but something else is feeding on the trees. Have your seen these beetles feeding? If nothing has been seen actually eating the leaves, try going out at nite as many insects are nocturnal.
Please submit another question with more details and I will be happy to assist you. You can also take a sample in to the Montgomery County Extension Office for a free identification. Their phone number is (409) 539-7824.
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