You could use the Sierra Chart plugin, but the Sierra Chart engineers have chosen to discontinue support for it at the end of the year. In fact, a prop trader asked me to make a Rithmic->SC bridge for this reason.

Anyways, Rithmic has a Google Protocol Buffers-based websocket interface. If you know how to program, you can always write your own Zorro plugin that connects to it. Or you can hire someone to do it for you. Or you can ask nicely on the forums and maybe Op Group or some other coder will do it for free.