When is created Business Central user with only rest-all role, no communication through REST endpoints is possible. When this user send request to the REST endpoint in Kie Workbench REST tests, the following exception is returned: javax.ws.rs.ForbiddenException: HTTP 403 Forbidden.
According to RHPAM installation documentation, user with this role can access BC REST endpoints. Usage of this role for REST and WebSocket was also discussed in JBPM-8337