While adding a second AD forest there is no possibility to mange this forest with regards to Server roles and it is not visible in Server Roles (Select Location) section.
A Feature Request has been submitted for the ability to assign Server Roles to users/groups from a different forest.
Symantec Corporation is committed to product quality and satisfied customers. Technical Support filed a Feature Request to add the functionality listed above. This Feature Request is currently being considered by Symantec Corporation to be addressed in a forthcoming version of the product.
There is no guaranteed date for this request from the Encryption Product Management team, or the Encryption Engineering team at this time. Please be sure to refer back to this article periodically as any changes to the status of the request will be reflected here. You can also subscribe to this article to receive notification when it is updated.
To have your organization added to the list of companies that desire this Feature Request, please contact technical support.