behaviour of tags

example.yml playbook

---
- name: Setup common tasks on all servers
  hosts: development
  user: root
  gather_facts: true
  roles:
    - { role: 'common', tags: 'common' }

main.yml

---
- include: setup_dns_resolution.yml tags=dns
- include: setup_logging.yml tags=logging
- include: install_useful_sysadmin_tools.yml tags=tools
- include: setup_nfs.yml tags=nfs
- include: setup_system_localization.yml tags=localization
- include: setup_shell_for_users.yml

playbook structure

├── roles
│   ├── common
│   │   ├── files
│   │   ├── handlers
│   │   ├── tasks
│   |.. |.. ├── main.yml
│   │   └── templates
├── example.yml

What I actually want to do is

% ansible-playbook -i hosts example.yml --tags "common,dns"

which should just run the DNS include from the common role...