As per this Google article
it appears Google is able to get your website subpage links from RSS files
It means it might be something like a sitemap (but not replacement). So thanks to a RSS, you may help google know about all subpages of your website
. But in order google find your RSS file, one need to link (do follow link) to this RSS feed file from the website. Another way to let Google know about updated RSS might be an "RSS submission". Just Google that..