>>>We have WIN SERVER 2003 as our Domain Controller in a single domain environment and we want to setup a server running WIN SERVER 2008 to operate as a backup domain controller in case WIN SERVER 2003 goes down. How do we set that up?
>>
>>Add the domain controller role to the server.
>
>In Server 2008 There are many roles listed:
>We have checked :
>Active Directory Domain Services
>
>What about the other roles, do we need them?
>DNS Server, Active Directory Certificate Services, Active Directory Federation Services,
>Active Directory Lightweight Directory Services, Active Directory Rights Management Services
>
>We will need this additional server to be our backup domain controller.
>
>Thanks

I would match roles with any that are on your current domain controller. Whatever roles your current domain controller has, you want them on the backup.