Add documentation about vars used in roles at the play level (#66907)

docs/docsite/rst/user_guide/playbooks_reuse_roles.rst

@@ -158,6 +158,8 @@ You can pass other keywords to the ``roles`` option:
 
 When you add a tag to the ``role`` option, Ansible applies the tag to ALL tasks within the role.
 
+When using ``vars:`` within the ``roles:`` section of a playbook, the variables are added to the play variables, making them available to all tasks within the play before and after the role. This behavior can be changed by :ref:`DEFAULT_PRIVATE_ROLE_VARS`.
+
 Including roles: dynamic re-use
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