Reusing tasks in Ansible
You can do so by either using roles: http://www.ansibleworks.com/docs/playbooks_roles.html
or by tagging individual tasks you want to be able to turn off: http://www.ansibleworks.com/docs/playbooks_tags.html
You can even combine the two, as described on the tags page:
You may also apply tags to roles:
roles:
- { role: webserver, port: 5000, tags: [ 'web', 'foo' ] }