Hi @Nerijus G,
Thank you for reaching out to us.
The reason you're not getting a stereo binaural mix (left ear isolated to the left headphone, right ear isolated to the right headphone) is because the individual channels are centered by default. I did some research online and unfortunately I was unable to find much information about panning individual channels on the Rodecaster Pro.
However, I did find this video below. This user was able to use 3rd party software to get the individual channels panned. They don't dive into the details until around 08:15: https://www.facebook.com/watch/live/?v=178128517507242
I would recommend reaching out directly to RODE to see if this option is available natively on the mixer.
I hope this helps. Let me know if you have any questions.
3Dio Customer Care