There are three steps to this. Below is how I found the RSS feed for one of my customer’s facebook pages: https://www.facebook.com/Bulldetailing

1. Find the facebook graph page for the site. For the example this is https://graph.facebook.com/bulldetailing. More generally it would be https://graph.facebook.com/[your-page-name]

2. Look for your id. On my clients’ graph page it is

"id": "176019295905837"

3. The RSS feed is then http://facebook.com/feeds/page.php?id=176019295905837&format=rss20. More generally it will be http://facebook.com/feeds/page.php?id=[your-id]&format=rss20