If you are using the Rose with Roon and now bypassing the built in DAC I would sell the Rose while it is still an in demand item on the used market and concentrate on a streamer only that is actually available to purchase. As the AirLens was a device originally conceived back when there was an input disparity on the Mk I and that disparity no longer exists on the Mk II then the field is wide open for streamer only devices that are available now. While the top of the line devices’ like Luca’s Innuos Statement, the yet to be released Pulsar or the Aries G2.1 would be preferrable there are plenty of satisfactory alternatives below them that allow you to use the now equal USB input. If you just feel the need to have an I2s input to compare then the Red and the Neo Stream come into play for much less than the last estimated cost of the AirLens. There are also alternatives in the price range in between like the U2 and the Aries G1.1 or even the Aurender N200 but they will not have an I2S option. For me a Mac Mini would be an option of last resort.
If I were in your shoes, I would keep the MKII & Rose until the burn in is complete. It doesn’t seem that you lose anything (other than a bit of clutter). There is something to be said about enjoying the MKII in all its glory in a system you are very familiar with.
This will then allow you to determine if the AL is that much of an upgrade from your current setup.
I think the MacMini as your streamer and Roon core is the least advisable. I remember when I used a MacMini and there was a good deal of noise produced by the computer. Things improved quite drastically when I cleaned up my front end (Roon Core, EtherRegen to optical ethernet, Signature Rendu SE). The only way I would consider this is if the BACCH software comes in to play (it may in the future).
I personally love Roon though, and if you are dead set on going that route, it may be feasible to get a dedicated, fanless Roon core (nucleus or intel NUC) and still go with plan A above. That is, keep rose until AL comes out.
That would be my vote. Hope that helps. Congrats on the MKII and welcome to the forum, I agree that it’s a lively and helpful bunch. Would love to hear your thoughts as time goes into the MKII 
The PSA streamer is aimed at a price point. The A Capella 3 is hand made to order one at a time with the best parts and case work available hence the price difference. Not judging anything just explaining the different approaches to an end.
No need for a Rose or any other device to buffer the USB if you use a Roon Nucleus. The USB is dead quiet going into the MKII and I have not even tried lifting the grounds as yet. I have stated this before as I have been using the USB directly out of the Nucleus for several years before getting the MKII. I hope folks will give this a try as it is a no cost option if you run Roon.
I am using my 3 year old Auralic Aries G1 via USB to MKII. I am amazed how the USB implementation on MKII has closed the gap on PST via I2S. Not the same but very close. What was perceived as my weakest link before is just not so today. I have no immediate plans to change out my streamer.
I like the Auralic as a one box solution that does everything I need. Has been connected with WiFi all this time with no issues and I really like their Lightning app. Not a Roon user, and reading posts here does not make me want to even consider it. I’ll give up some bells and whistles for simplicity. The Auralic just works, and works well.
I find it interesting that folks think Roon is complicated? I guess it can be if you run it on oddball equipment, connections and other weird stuff., but a Nucleus with a reliable Ethernet connection and USB into MKII is a no brainer.
Agree with @DennyD re Roon. When I purchased the Rose 150b, I did so motivated by the reviews of the OS interface ease of use. I needed a network streamer, not so much the internal DAC and found the Rose to fit my needs a year ago for that purpose. I was not aware of the existence of Roon at the time I purchased the Rose. After a recent introduction to Roon by a fellow audiophile and trial run on Roon, I purchased a lifetime subscription finding the app more intuitive and stupid simple to operate. I just want to listen to music in the best format available with minimal fuss and Roon surprised me with how easy and useful it is to operate. The metadata information provided by Roon on the tracks, artist, album are just amazing and appreciate seeing how the music is converted along with format and quality within the app. Very handy. I don’t use the Rose OS via iOS other than to turn the Rose screen on or off remotely. Had I understood how easy Roon works with Qobuz/Tidal and owned music files on a 2013 Mac Pro hard wired into my network and working as a music server, I probably would not have purchased the Rose.
About 10 hours into the Mk II using the Rose as the streamer connected via USB. I tried the Rose DVI to Mk II HDMI thinking I2S would work. But the Rose Software forced use of the internal DAC, inverted the polarity, and screwed up the phase. Switching from the DVI to the USB A out of the Rose and into the Mk2 USB B ($10 USB cable from Best Buy LOL) in provided jaw dropping SQ and info not previously noticed on DSD 256 tracks. If additional burn in expected to provide greater SQ, I am not sure how as the music sounds fantastic as is. I have not lifted any of the grounds to take advantage of the galvanic isolation as the speakers are dead quite at present and no ground loop noticed or hint of a hum. An AudioQuest Coffee USB 0.5m cable arrives Saturday and will replace the Best Buy printer grade USB. But even the BB USB cable sounds pretty darn good. I may just plug the AQ Coffee into the back of the printer to see how much more vibrant the colors are LOL.
Great stuff!
I wish Rose made the big display of the 150 in a streamer only. I dont want to pay for a dac
If you do, the Front Range hosts a treasure trove of high-end audio manufacturers 
PS Audio - Boulder
Boulder Amplifiers - Louisville
Sanders Sound Systems - Conifer
YG Acoustics - Arvada
Ayre Acoustics - Niwot
Rowland Design Group - Colorado Springs
At this point, if I were to get another streamer, something I could feel comfortable that I could have for quite a while, I’d get the Musica Pristina A Cappella III. Yes, it’s expensive. But it’s built with the best components and you can get both isolated I2S and isolated USB. That’s about as futureproof as I’ll need.
That said, I am 80% of the way through my normal procrastination cycle to getting the BACCH4MAC.
Peer pressure and FOMO are a b____h.
If you look in “Your Next Upgrade”, you’ll see why I am procrastinating.
Why not mount the beast between your speakers along the front wall on a perch at the proper hight for mounting the BACCH camera?
There is a plethora of DACs without Streamer
But slim choices for Streamer without a DAC. All I have found is iFi Zen for $400, Holo Red for about $1,100, and Capella for $5,500. (the Holo Red is either a DAC or Streamer, but not both without 2 units)
On top of this, I’m probably trying to find a Streamer-without-DAC that does not require Apple AirPlay or noisy USB connection for Audirvana, which is producing best sound for me even via AirPlay compared, for example, with Roon
Update: hereby announced is that I was wrong; there are many streamers. I don’t want to hear them, or else I might have to realize the worth of big spending.
Actually, the “Red” can function as a “streamer” or a DDC, but not as a DAC.
FYI.
I just got the red for $850
memory is a fleeting thing
oh my, still need a connected DAC!
I see $798 on site, though tax and shipping too