Run included ansible task as standalone task

There are two requirements to achieve this:-

1. the host you're trying to target must be in an inventory file

2. you need to tag the tasks in the role you want to run

   - name: Add user me
     user: name=me comment="Me" uid=9999 groups=somegroup
     tags: this_role
   - name: Add my ssh public key
     authorized_key: user=me key="{{ lookup('file', 'id_rsa.pub') }}"
     tags: this_role
   

Then you can:-

ansible-playbook foo.yml -i hosts -t this_role --limit host.example.com

Not that this is still running the playbook that contains the complete play, but it's limiting the tasks that run to just those that match the tag. The remaining tasks will be skipped.