Are there other books than the Core Book? Such as a book containing the Roden race?
The Roden are in the Monster Burner, which is out of print, as are the Magic Burner and Adventure Burner. There are no legitimately available PDFs, and there won’t be in the foreseeable future. As of right now, there aren’t any plans to reprint them, as far as anyone knows.
The quick answer is no, there are no other books.
So I cannot play a Roden in Burning Wheel Gold?
If you are able to find a copy of the Monster Burner floating around in a LGS or being sold on Ebay or Amazon or wherever, you can easily convert the Roden race from BWR to BWG. The trick is of course actually tracking down the Monster Burner with which to make the conversion.
You can also make your own rat-people pretty easily by tweaking existing BWG races. I think BW has a strong DIY vibe. I know that’s not always a satisfying answer, but I’m sure help is available on the forum for this endeavor should you need it.
Another option, announced today by Luke. The Burning Wheel Codex is being released and Kickstarted as I type this and it is only $250 away from funding… Follow the link to the promised lands. https://www.kickstarter.com/projects/burningwheel/the-burning-wheel-codex
Why no life-path creator?
The monster burner has advice on burning up lifepaths. I assume this material will be included in some form in the Codex under the auspices of “detailed commentary on nearly every aspect of the urtext itself”.