Turns out I was simply using a wrong command line to run the playbook: ansible-playbook -i inventory.yml tasks/main.yml
instead of ansible-playbook -i inventory.yml playbook.yml
.
After that the error messages became much clearer and my final playbook looks like:
---
- name: Play
hosts: all
become: true
roles:
- /home/marco/play/roles/ics-ans-orca-driver