You can add organization administrators to vCloud Director individually.  You can also add and modify the roles that determine what rights a user has within their organization.

*Important* You must be an organization administrator to manage the users, groups, and roles within your organization. Your system administrator can publish one or more global tenant roles to your tenant, and as an organization administrator, you can see them in the list of roles. Such roles are: Catalog Author, vApp Author, vApp User, Organization Administrator, etc. 

You cannot modify the predefined global tenant roles, but you can create and update similar custom tenant roles and assign them to users within your tenant.