Let's say your playbook wants to use the "foo" role.

---
- hosts: all
  roles:
    - foo

By default, roles_path in ansible.cfg is commented out.

# roles_path = /usr/local/roles

When commented out, Ansible will search the following directories for the "foo" role:

• The directory that contains your playbook (e.g. /home/john.doe/foo)
• /etc/ansible/roles/foo

Let's say you define some other roles_path in ansible.cfg.

roles_path = /usr/local/ansible/roles

Now Ansible will search the following directories for the "foo" role:

• The directory that contains your playbook (e.g. /home/john.doe/foo)
• /usr/local/ansible/roles

It is noteworthy that you have a role that resides in some other directory, say /usr/local/testing/roles, the role can be used by including the absolute path to the role in your playbook.

---
- hosts: all
  roles:
    - /usr/local/testing/roles/foo