Kinsky is free open source DLNA/UPnp "Control Point" software for iOS, Android, Windows, Mac, and Linux. It works for sending individual songs from a DLNA server to a ROCKI but it appears to require "State Eventing" to monitor playback and change tracks. Does ROCKI support "State Eventing" or plan to in the future?
One feature of Kinksy is the ability to support separate playlists for different "rooms," but without the ability to change tracks, it is not really very useful..
My ultimate objective is to be able to run a program on a Windows computer to send music to multiple ROCKIs (either the same stream to all devices or separate streams for each device) using an iOS device as controller. Since I run a DLNA server on my WIndows server, the Kinsky software is a good start, but the "State Eventing" would have to work and it does not appear to support a single playlist for multiple "rooms."
Main site: http://oss.linn.co.uk/trac
Description of UPnP features: http://oss.linn.co.uk/trac/wiki/UPnP