---
- hosts: notebook
  vars_files:
  - ['secrets.yml', 'secrets.vault.yml']
  - vars.yml
  roles:
  - common
  - notebook

- hosts: proxy
  vars_files:
  - ['secrets.yml', 'secrets.vault.yml']
  - vars.yml
  roles:
  - common
  - proxy

---
- hosts: notebook
  vars_files:
  - ['secrets.yml', 'secrets.vault.yml']
  - ['vars.local.yml', 'vars.yml']
  roles:
  - common
  - notebook

- hosts: proxy
  vars_files:
  - ['secrets.yml', 'secrets.vault.yml']
  - ['vars.local.yml', 'vars.yml']
  roles:
  - common
  - proxy

Allow vars.local.yml to override vars.yml.
Allow vars.local.yml to override vars.yml.
