@Neil Watson
You can with following REST API call
curl -u admin:admin -H 'X-Requested-By:admin' -X PUT '<a href="http://localhost:8080/api/v1/clusters/cc'">http://localhost:8080/api/v1/clusters/clustername'</a> -d '{ "Clusters": { "desired_service_config_versions": { "service_name" : "HDFS", "service_config_version" : 1, "service_config_version_note" : "REST API rollback to service config version 1 (HDFS)" } } }'
In this service_config_version - is the old version you would like to revert to.