I've got a Roadster 2, with the base JVC 900 head unit.
It comes with a bluetooth adapter that you can plug in to one of the USB ports. It works fine when I pair it to my phone for voice calls.
But when I try streaming music from my iPhone, it doesn't work very well. It connects, controls the player, and plays the music--but it "skips". Roughly once every three seconds, a small (maybe 1/4) second piece of the music is missing. You have no problem telling what song it is, but boy is it annoying.
The iPhone streams music just fine when I pair it with a Motorola T605 bluetooth controller in another car. I have tried both USB ports on the JVC. I have the iPhone about a foot away from the bluetooth adapter; but I moved it back and forth a bit with no change. I have tried shutting everything off and restarting, but same behavior. There were no other bluetooth devices in the vicinity.