Hootsuite is a platform that's designed to bring all your social media posts, replys, comments, etc. under one roof (or window, actually). Part of that is the posting of items from your RSS feeds to social media. This functionality is similar to Buffer. See our article about them. It's about the same drill, set up your social media accounts, your RSS feeds and post away. I've used Hootsuite a bit and I don't like its user interface as much as Buffer, but it does other things that Buffer doesn't. The moral of the story as always: do your system requirements. List out what you want your social media management tool to do and do an analysis of which tool fits your needs best.
Pricing is free, $9.99 per month, and up. How far up? Their website is pleasantly vague on that.