Ansible with Packer, root

I am using Ansible 1.9 and Packer to create and install new package on a Debian VM.

Packer run my playbook, but the installation of the package fail because I am not root.

Can anyone give me an example of a playbook which install a package on a Debian ? (With of course the possibility to be root in order to run apt-get install)

My actual playbook (which is not ok) is the following (I install fortune for a basic example)

hosts: all
user: root

tasks:
apt: name=fortune state=installed

Thanks for any help

tasks is list, so each one needs to be preceded by a dash '-'

hosts: all
user: root
tasks:
  - apt: name=fortune state=installed