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Is it possible to take room measurements with adi2 dacfs

Of course it is possible. But not with an analog Mic directly connected.

Read here:
https://www.roomeqwizard.com/help/help_ … xplanation
-> Cheapest way: Buy a USB microphone (miniDSP UMIK-1) that comes with a calibration file as REW Manual recommends

and here:
https://www.roomeqwizard.com/help/help_ … d.html#top
-> recognised USB microphone that has REW-compatible sensitivity cal data, as of September 2022 the UMIK-1, UMIK-2, UMIK-X, EARS, CARIO-A2B, UMM-6, Omnimic and Beta Three mics are recognised

Buying a 2nd Soundcard just for Measurement is unnecessary in my mind.
If i look in the ascii drawing: BF could probably do the same without the ADI-2 DAC FS at all (I am not sure)?
And would cost around 1000€ (BF Pro FS plus ECM-8000).

If you follow the recommendation from the REW help above, UMIK-1 is fully supported there.
And would cost around 100€.

Yes, first option... Regarding your further explanation, just let other readers decide themself how to interpret this. 

"will" - dont know what if you meant my post 6 or sth further?

Regarding your link to the youtube video: As i understood this - he doesn't measure anything.
Its just like playing some sine waves/ variable frequencies from REW via speakers and listen "by your ears" if something in your room makes noise due to resonance etc...

Edit: Oh, i just noticed, later in his Video he uses a SPL Meter (what is some kind similar to a whatever mic). But - who has a SPL Meter at home? I personaly only got a few times in touch with these when the Police stopped me to check if the „db-eater“ of my motorcycle was accordingly installed ;-)

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Anyhow, i try to share just my personal experience. I should mention, that i do this all with REW. No guarantee, if i understood everything correctly! But thanks for correcting, if i msunderstood sth.

Afaik i understood the whole roomEQ (for supported RME units) / pEQ (for the ADI-2 x units) sense - please correct me if i am wrong - the final goal of a measurement is to get the individual "overall" measurement (included room/position/speakers/monitors and all the hw related stuff, etc). And finally a .tmreq/.txt or .adieqpr file will be dropped, which you can import into the unit.

Fact (afaik): To get a real frequency/SPL measurement (where you can adjust the pEQ filters in REW afterwards) you always need to send a signal (from your speakers) and record it (via whatever mic).

If you want to use a "normal/usual" Mic for this, you need:

1) First measurement: A soundcard where you can do a loopback via connecting a physical cable from out to in (not a digital loopback via TM FX) to get the freq response measure (soundcard calibration) of its DA/AD converters

2) Next measurement: A Microphone plugged in to the sondcards Input and (IMPORTANT): A mic with its individual calibration profile (= the mics frequency response cure). This profile can be a imported as calibration file (provided with "measurement mics") or if you use a "normal" mic you can also provide its response curve via a a csv/txt file abbreviated from its data sheet. Of course, this is usual not as precise as the "measurement mics". (But in my case enough as a starting point to get deeper in this)

F. ex: I tried with a old tbone. I just found this poor graph for it:
http://recordinghacks.com/pdf/tbone/dat … uk_web.pdf
(a shame - no dB values, no frequencies, provided - but this was what i had, and i put some things together... 
... and used a free online tool to get the values as a csv from its diagram:
https://apps.automeris.io/wpd4/
imported the results in REW to get its response values...

You cant use a "normal/usual" Mic for this, if you are not able to connect it to the input to do a physical loopback or connect a Mic to the input of the soundcard

1) If i understood the REW docs right, the only way out is a USB Microphone for this (as i already described)
2) afaik - latencies, etc, due to this are compensated by REW for measurements. So regarding room measurements this should not really matter.
Edit 2:
But - if you also want to be able to adjust the delays in roomEQ accordingly - you will surely have to involve the latencies, and the distance from mic to speakers in the whole calculation.
-> this will be my next exploration. I ignored this until now.

I think I know now what you mean.
I didn't expect that you read my questions in a 1st draft of my posting so quickly yesterday,
as I removed it them quickly within a few minutes,

I redecided to ask the company which sells the Behringer Mics with REW measurement profiles.
The intention was to save you work, if I call them anyway by phone.

BTW .. I do not know any USB measuring mic with a clear measurement profile in numbers
where it is easy to get the values from a logarithmic frequency graph.
Therefore my recommendation to look for a better solution.

To chime in on the topic: For Room EQ Wizard I can actually recommend the miniDSP UMIK 1 USB Mic rather than a XLR one (or one of the other USB mics linked above).
Of course this comes with a calibration file as a simple txt file. See also here: https://www.minidsp.com/applications/ac … w#calfiles

More importantly, I find it more beginner friendly to use with ROOM EQ Wizard, as it is already SPL calibrated (through its built in fixed level preamp...).
If you connect a regular XLR measurement mic, there is no way for ROOM EQ Wizard to know the actual dB SPL, as it's dependent on the preamp level set in the interface.
Thus, measuring with a calibrated dB SPL meter is needed to set it up properly (or a modern smartphone's dB measuring app might give surprisingly accurate results, if used correctly).

For the easiest beginner friendly solution, which does not require much knowledge or reading, something like Sonarworks (with their measurement mic) or Dirac Live will be easier to set up than ROOM EQ Wizard. Measurements taken with Sonarworks can also be exported to RME's room eq. Afaik there is currently no export from Dirac Live to RME Room EQ.