The Operations Manager Product Team posted a good article explaining the role and purpose of the SCOM Root Management Server (RMS).
Microsoft could do better in the business continuance/disaster recovery arena by providing a simple wizard to automate the promotion/demotion of the RMS.
In my experience, most DR scenarios usually involve a site failure (power or network) that simple clustering won't resolve. The steps required to failover to a remote site (importing the RMS keys and updating the agents) currently require someone with sufficient rights to follow a separate DR procedure document. It would be nice if this could be done from the GUI (where most of the admins live). This would facilitate the DR process when resource and time constraints are most critical.