It's a dead format, but check this sitemaps comparison article if are still curious. No search engines support ROR extensions, but yes, the files are read since ROR basicly just extends RSS.
Use of ROR file is nothing it is just help full to provide your title and meta tag information for the search engine.
This free tool will crawl your website and generate a ROR Sitemap with up to 1,000 URLs for ALL search engines, not just Google. ROR is a rapidly growing XML format for describing any object on a website (sitemaps, products, services, menus, images, reviews, contact info, business info, etc), so any search engines can better understand its content.
Can you provide a link to any page on Google, Yahoo, Bing or any other major search engine that list ROR as accepted format e.g, Google mentions xml sitemaps protocol, url list text file, RSS, Atom and other. But not ror.