Given that it is not possible to have multiple zones using a single endpoint, despite the feature request (One Device, Multiple Speakers/Headphones or By-track, by-album or output device DSP settings) being raised several years ago, I have stopped using DSP for my headphone listening with Roon.
I found that after applying the DSP on the source endpoint for Headphones, I would forget to remove it for Speaker listening and then panic that something had broken.
Plus after making some upgrades on my source (2nd power supply for the Naim NDS network player) I am preferring playback via the Dan Clark Audio Aeon2 Noire’s without any EQ.
I still use ‘FR per headphone’ type on ARC, but there you can save different presets on the phone depending the listening mode (with doogle DAC, in-car, etc.)