Regardless of the brand of your SoundBridge being RoKu or Pinnacle, uPnP servers should be supported.
Twonky is one of those, but its not free.
There is preliminary uPNP server support in firefly at this stage, but it is not aimed at the featureset you’d like to see.
I really can just google for upnp server myself there, so… *shrug* 🙄