The settings @Mikael_Ollars show are in Roon but control the quality of Qobuz, you need to look in Roon under Settings >> Services and press the edit button next to “Qobuz” then check the first image against your settings:
Many thanks @Mikael_Ollars
FWIW I’m a Qobuz HiRes user but it’s not easy to spot the difference between Redbook CD at 44.1/16 and higher res content.
Here we are: I don’t have the Hi-Res option in Roon settings.
I had to unlog and relog Qobuz.
It seems to be ok, now.
It works! thanks for your help.
Now, how could I switch between CD quality and hi-res quality in Roon?
I need to test if I can hear any difference…
Just play a cd quality version of the same file if there is one choose from the versions tab on the album. If not you need to lower the quality setting shown above.
But those are different masters? Comparing apples…
The only reasonable comparison would be using the selection of streaming quality in Roon. I suppose that Hifi-subscribers have access to the same material as the Sublime + subscribers, only in lesser resolutions.
I can see same master on some albums at cd and hires, obviously you need to use same master.
I have used the settings of Qobuz (in Roon) for my tests. So, same CD, with different settings in Roon to compare.
Honnestly, I feel that if ever I can hear a difference, this is not that much.
Yet, not sure I have chosen the appropriate CD. Any idea of CDs where you feel that we can really hear a difference?
Tbh not many I can think off that do in my humble opinion. A good recording is way more important than bitdepth or samplerate. If you don’t hear a difference then I wouldn’t trust any body else’s opinion than your own and save the money.
Well, I do detect a difference (or I think I do), but I don’t think it worths the money so far.
But the question is: for a “good recording”, can you enjoy the difference between hi-res and CD quality?
Not sure if you want to change the music style, but if you want to hear some differences, check out a few Pearl Jam (Ten, Vs., Vitalogy, Gigaton, etc.) albums and change the settings in Roon, as you did with this album. I believe that the quality of the recording and dynamic range on these albums creates an audible difference when listening to the Hi-Res vs CD version.
Choose a few different artists or music styles, as one album usually won’t give enough weight to make this decision.
How do you know that? Genuinely interested! 
As i understand. the Versions available in Qobuz (or Tidal) are different issues and hence, mostly different masters.
Same release dates (not original release date). Tidal have the same releases as MQA and regular at the same time. Just having hires tier does not exclude you from using the cd version.
Probably too broad a statement. Some albums are just down sampled, some albums are different masters. It is going to depend on the Artist, the Label and the Producers/Engineers that all decided what they wanted the album and recording to feature and present.
Sometimes it about the sound and the music. Sometimes it’s all about the money, and having low, medium, high and ultra high-res versions means more individual sales. Not nearly as relevant today, but still exists.
Also you can check the product number of the release. It might have a slightly different one for the hires version if released at same time or be the same. Just like cd releases have a catalogue number.
How many of the Hires files are just up sampled CD’s? I don’t see info saying the producers used the original master tapes. If the music is good I’m happy.