The Roland Rubix22 does not support loopback.
The Rubix24 and Rubix44 support loopback.
How loopback works (Rubix24, Rubix44)
When the [LOOPBACK] switch is turned on, the audio signal from the INPUT (1L, 2R) jacks is mixed with the audio played back from the computer, and this mixed signal is sent back to the computer. On the Rubix44, the INPUT (3L, 4R) jacks are also included in this mix. Use this function for live broadcasting to the internet.
Note: When the [LOOPBACK] switch is on, turn off the monitor function in your DAW software and the monitoring function in Windows. If you do not do this, you may hear oscillation (feedback) or doubling of the input sound. For full signal routing details, refer to the Rubix22 / Rubix24 / Rubix44 Reference Manual.