Available roles in a Plone site can be queried by interacting with the /@roles endpoint on portal root (requires an authenticated user):
To retrieve a list of all roles in the portal, call the /@roles endpoint with a GET request:
.. http:example:: curl httpie python-requests
:request: ../../src/plone/restapi/tests/http-examples/roles.req
The server will respond with a list of all roles in the portal:
.. literalinclude:: ../../src/plone/restapi/tests/http-examples/roles.resp :language: http
The role title is the translated role title as displayed in Plone's
"Users and Groups" control panel.