Now that Roon runs again on my main control, I finally had time to look into this by myself.
System: Ubuntu 18.04.6 LTS, Linux 5.4.0-120-lowlatency, wine-7.0, Intel® Core™ i5-6400T, Lenovo ThinkCentre M700 SFF
I see roughly the same figures reported in top as shown in the OP. Is this a problem for me? No, not at all. Looking at the system monitor graphs, having Firefox running with usually a dozen tabs open already creates a substantial load and opening Roon doesn’t add that much to it as the numbers might imply. The load shows neatly distributed over all 4 cores. Despite the fact that this is a small form factor PC, the fan runs civilized and barely noticeable. I could still close Firefox to reduce the load (significantly).
My conclusion:
Based on the nature of the Roon UI, Roon always used more resources than other, *normal" dektop apps.
Click on the picture to go the source posting.
Now even upped to 120 fps (on supported systems only?) may have made it use even more resources, but this seems to be part of the game (continuous development of the software, adding support for new hardware) and likely unavoidable.
Fun fact: I once installed and run a “real” game (Steam Proton so using Wine of some sorts) on this machine - for five minutes. After that time I had enough of the turbine sound the fan produced.
Skimming through this whole thread again, it seems the major complaint is not about the higher load per se, but the accompanying circumstances (audible fan noise). So affected users should maybe investigate if there are options available to optimize load balancing/power saving/fan (speed) control on their machines.
Note: Using Lenovo (former IBM) laptops and now this SFF PC, I made the experience that a lot of effort was put into proper Linux support for the premium Think-range of products. Maybe this is why the fan behaves so civilized right out-of-the-box on my machine compared to the machines of other users here?