Damian,
I believe you have made your physical host running Windows Server 2012 R2 Essentials as a Active Directory Domian Controller and a Hyper-V host. The setup is failing because it detected the Domain Controller role on the machine.
ideally we recommend that you do not run any other roles on a server that is configured as a Hyper V host (See the following link
http://technet.microsoft.com/en-us/library/ee941145(v=WS.10).aspx )
For Windows Server 2012R2 Essentials Deployment the recommended deployment mode is
1) On the Physical Host enable only the Hyper V Role
2) Run a VM inside that host where you enable the Server Essentials Role.
Regards,
Anoop KV