Planning for RODC?
Before any implementation have a look at this updated guide at:
RODC) Branch Office Guide
This guide describes new features in Windows Server 2008 that can provide benefits for Active Directory deployments that include branch offices. It explains how to assess an existing deployment of domain controllers in branch offices to determine whether deploying read-only domain controllers (RODCs) in existing or future branch offices is appropriate for your organization. For more general information about how to install and configure an RODC, see Planning and Deploying Read-Only Domain Controllers. For more information about deploying an RODC in a perimeter network (also known as DMZ), see Active Directory Domain Services in the Perimeter Network (Windows Server 2008).