_DOMAINROLE — Returns a string describing the computer’s network role.

Syntax:
%_DOMAINROLE

Possible return values include:

Standalone_Workstationnot a member of a domain
Member_Workstation 
Standalone_Servernot a member of a domain
Member_Server 
Backup_Domain_Controller 
Primary_Domain_Controller 
Unknowncan’t happen?

echo %computername is a %_domainrole.