query on common elements and includes

app.yml

---
- hosts: app
  roles:
    - common
    - httpd
    - { role: vmware-tools, when: ansible_virtualization_type == 'VMware' }

dep.yml

---
- hosts: dep
  roles:
    - common
    - tftp
    - xinetd
    - httpd
    - pxeboot
    - { role: vmware-tools, when: ansible_virtualization_type == 'VMware' }

mdb.yml

--- 
- hosts: mdb
  roles:
    - common
    - mysql
    - { role: vmware-tools, when: ansible_virtualization_type == 'VMware' }

xen.yml

--- 
- hosts: xen
  roles: 
    - common/ntp
    - hp-agent
    - xen