I think you meant to say reaper not reason in the first few lines.
At the moment renoise does not announce midi ports to the rewire master and you must use a virtual midi port (there are many free available, I use loopmidi). However, as as far as I know, you must always specifically select a specific midi port that the rewire master will send midi to from a track in all daws, it will never play as is, unless an instrument is the first in the list or the only one available.
You can of course set that virtual midi port as the master keyboard in renoise preferences. But I don’t think that’s what you want.