Two weeks ago I converted the Roon Core OS on Linux Ubuntu installed on a NUC11PAHi5 to Roon ROCK. I must say that i am really surprised that Roon ROCK sounds much better than Roon Core - streaming from Qobuz.
Low bass is deeper; imaging/vocals is more solid and dense; sound is more dynamic. Everything seems to sound louder and more solid at the same preamp volume level. Could this apparent improvement in “sound quality” be due to a higher USB digital output from the ROCK software, thus making the sound louder and more dynamic? I have experienced that using the Roon server software with Squeezebox player software on a dedicated Streamer sounds less loud compared to using Roon server and player softwares.
Has anyone noticed any sound quality differences when converting from Roon Core to Roon ROCK on a NUC11?
Like a veil being lifted and your wife telling you from the kitchen what did you do to achieve such and amazing sound?
Sorry, like dolores o’riordan stated, it’s in your heeeead, in your heeeeead 
Bass comes from your woofer with a little help of your amp. Not from your usb output.
Assuming that the signal path is the same in both situations (and possibly that you do not use DSP), it would be very strange to have sound differences, both in quality and in volume.
Even using DSP (with the same settings), it would still be very strange to have differences.
I did the same type of conversion (but in the opposite direction, from ROCK to Linux) and I did not notice such differences (this with two different DACs).
The signal path is exactly the same, with no DSP or other signal processing. USB output from the NUC11 to a MSB Pro USB module (both located in a closet), which is then connected by a fiber cable to the MSB Reference DAC in the listening room 10m away. I am surprised by the sound quality difference because i didn’t expect any difference. A friend came over to listen and said that the sound performance has improved. Bear in mind that different streamers/servers in the market do sound different due to how the Roon Server and Player softwares are implemented in their machines.
As you have detected a SQ difference in Linux builds you now have no option but to try at least half a dozen different distributions to see if any sound better than the custom ROCK build. Do let us know how you get on, especially if you find something that is ‘so much better’ once again than ROCK is currently.
The NUC11 Linux Ubuntu based Roon Core is already very good. I had home demo’ed a few reputable and expensive servers/streamers and compared them to the NUC Ubuntu Roon Core, and the SQ difference is very small or indistinguishable. I performed A-B blind tests for an audiophile friend, and he had a hard time distinguishing the difference and thought the NUC Roon Core sounded better!
This maybe because of the MSB Technology Pro USB-ISL modules interfaces that converts the USB signal to optical signal which is synchronised to the internal Femto clock in the DAC.
I always remember the SQ differences I encountered when using Roon in the beginning. This was on the same NUC with different software (Daphile on its own, Roon on Windows 10 and Roon on Ubuntu server software. They weren’t huge (except for whatever reason Daphile was very poor back then). This was using USB to connect the DAC. Using Roon in various OS environments did yield some differences in my mind but they were subtle. When Roon finally launched ROCK I tried it and never went back.
shhhh… don’t say it too loud, just enjoy the effect of before you get used to it and it goes away… 
Next thing U need are audiophile network switches…just kidding. All nonsense stuff
Don’t forget about gold plated ethernet cables and tuning weights…
I don’t play with gadgets, but i do believe in good neutral cables and the most direct signal path - digital or analog. I have a quality ethernet cable direct from the main home fiber optic modem/router to the NUC and a good USB cable to the MSB Pro USB module. And a normal fiber cable connects to the DAC.
You can belive in what you like most. Even in god. Sound is another thing. Don’t worry, it’s a path we all go trough our audio journey. Some wake up, some never understand it.
Here’s a non-snarky response (I know, they are rare in these forums).
I did the same move a few years ago, changing nothing else. I really couldn’t hear any difference between the two. If you did, and you’re happy with the outcome, then that’s great.
Thanks. Actually i was a bit worried that converting to ROCK would negatively impact the SQ, but it did not. Maybe i am imagining things, but that is okay as long as i didn’t imagine that the SQ is worst. Like you said, as long as i am happy that is great. I have been in this hobby for over 40 years and have never been happier.
The only time this happens to me is because there is a volume difference. Even half a dB can make a very large difference. Volume matching is typically the toughest thing to accomplish when you are AB or ABX testing.
Never tried it, but I’d be almost as surprised to hear a difference as I would switching to boutique AC power cords.
But, if the core is the only thing changed, there should be no volume difference. Bits are bits. Unless some sort of DSP is enabled in at least one of them.
…and make sure your Ethernet cables are isolated from any bad dielectrics, using boutique cable lifters.
Have you checked if you have Volume Leveling enabled or disabled between the 2 configurations? That may cause a change like what you are describing.
I had a similar experience once a couple of years back when experimenting with different streamer hardware going into my DAC. I was able to A-B between them using the Transfer Zone feature of Roon, and as I switched to the one I thought “should” sound worse, it sounded better! Like you, I wasn’t changing the volume on the preamp, but it sounded louder and more dynamic, more solid bass etc.
After transferring back and forward a few more times, yes it definitely sounded better.
Then I compared the settings for the 2 zones to double check I was comparing apples with apples…
There it was, the “better” zone had Volume Leveling turned off and the “worse” zone had it set to Auto, and Roon was volume leveling down a dB or two on the song I was testing on the “worse” zone…
As soon as I turned Volume Leveling to Auto on the “better” zone’s device config, I could no longer discern any difference between the 2 zones 
In my system I have listened to the Antipodes K50 music server using the USB output to the MSB Pro USB module which converts the USB signal to a fiber optical signal. The K50 is a server & player with a few server apps and a few player apps to choose from in whatever combinations you want. The K50 can work with Roon as server and player or Roon as server with Squeezelite as player. I have listened to the two combinations of server/player apps, and the Roon server app with Squeezelite player app combination clearly has a lower sound volume level. The lower volume level when using the Squeezelite player may have resulted in the sound to be perceived as less dynamic and smoother. The is a significant sound difference between using Roon player and Squeezelite player. I did not attempt to match the volume level of the Roon player and Squeezelite player. The message here is that different proprietary player apps do sound different whether it is due to the different output volume of the USB digital signal/bits or the different operating systems used in the different players apps. 