If you have the RDC6445S controller (NOT G) then this might just be your lucky day.
Here is my link to the Firmware for this controller
There are 2 Firmware versions - V26.01.13 and V26.01.16
.13 will run your rotary off the U Axis.
.16 will run your rotary off the Y Axis.
Firmware has to be upgraded through RDWorks
I have added a 3rd Axis driver to my machine and all rotary settings are set up on that U axis, so no more swapping settings and connections on the Y axis!
Here is a video of my setup and a quick guide how to change the controller settings to run the Rotary direct.
I hope this is of help.