During Xmas I had some more time to listen and experiment. I borrowed simple AC filter with 5 plugs and also some high-end power cables. And wow, the unpleasant tin sound of highs is gone. I still hear difference between streaming via ROON vs. directly to BluOS card, but now it is favorable to ROON, as it shows more details and sound is more “live”. The only drawback is that only well recorded tracks sound good. Many other recording suffer from unpleasant sibilance, which now my system presents ruthlessly. But I double checked this on headphones and this is just bad recording or mastering.
So, my apologies to ROON RAAT, the problem was somewhere else.