A method was found for cap-add but it does not have the right parameter type. Skipping it. You may want to add a feature request.
And here, you have examples of Roboconf components / scripts that manage Docker containers. https://github.com/roboconf-recipes/docker-cassandra-cluster/tree/master/src/main/model/graph/cassandraNode/scripts
This is how I manage Docker deployments now with Roboconf.