Roost Circles is a feature within Campaign Creator that allows you to leverage others' social networks through content sharing. With Roost Circles, you join together with complimentary businesses to cross promote & cross market each other.
Roost Circles is a great way to jump start your social marketing efforts. You may have a limited number of Facebook Fans and Twitter Followers, but by joining together with others, you immediately have access to more people than you would have on your own.
After you have invited others to join your Roost Circle, you will be able to prompt them to share your content with their network. You are also able to quantify your reach as well as your combined outreach through your Circles.
Likewise, the members of your Roost Circle will prompt you to share their content. This is a great way to get more content in front of your users and build your fanbase.