T-Mobile offers its customers something called Music Freedom. This allows a user to stream music from their preferred music provider without impacting any total streaming quota they may have in place (e.g 100gb).
Notables missing are Roon Arc and Qubuz. I don’t know what the financial burdens on the streaming service are, but I would think if Bandcamp, SomaFM, and SoundCloud qualify then Roon Arc could as well?
Bottom line. Including Roon Arc would allow me to stream unlimited amount without using up my monthly quota of 100gb.
As far as Roon ARC is concerned, it might not be so straightforward not least because the music, when streamed from your Roon Server, is not being downloaded from a source known to T-Mobile and Identifiable as a music streaming service.
Also, the streaming protocol is likely a Roon protocol and so may not be identifiable as music in the same way as the supported streaming services.
Given Roon really isn’t a well known service outside its userbase of way less than 500k I doubt they know of its existence or would add it as it’s not worth the admin. I have a 12g allowance and never used it up once. But I don’t see the point of lossless on the go, you can’t hear the difference with all the noise even with nc which your then using lossy anyway.