If you're talking about DNS servers that should be defined under pools.yaml (via variable designate_pools_yaml) then yes - they should be installed additionally. Eventually, Designate does support more backends then just Bind9 [1] and they're usually deployed outside of the designate containers or even OpenStack control nodes. So as OpenStack-Ansible we don't provide a roles/playbooks to install this kind of infrastructure. But there're quite a lot of good roles on galaxy.ansible.com that provide bind9/pdns4/etc installation.