The task Create directories ignores directory variables, and should look something like:
file:
dest: "{{ item }}"
state: directory
owner: "{{ nomad_user }}"
group: "{{ nomad_group}}"
with_items:
- /opt/nomad
- /var/run/nomad
- "{{ nomad_data_dir }}"
- "{{ nomad_config_dir }}"
- "{{ nomad_log_dir }}"