I just decided to give this a try tonight. It was suspiciously easy, which makes me think I did something wrong.
But they work in the game as far as I can tell, do not make other roof texture options disappear, and are preserved through reloads.
What is not easy is working with the crazy template for these textures, thus they aren't the world's most beautiful rooves. But if they work, I can explain to people with more patience than me how to recreate the files.
The rusty corrogated metal roof will only look right on a Gabled style roof, not a Hipped style roof. That's due to the way vertical patters align, not because of a problem in the file.
Other than that, please let me know if you have any problems with them and do not post these to another site or start sharing any new rooves based on them.
Wait until they have been tested for a while. They may conflict with something that I've just not noticed yet, so give it some time.
Thank you to rentechd for giving me some roof textures to test with.
*Updated to add the Red Cedar roof, 28 Jan