Over 10 years I am watching this topic and contributing to it. I see that HQPlayer PCM to DSD on the fly conversion is widely considered to be the best available.
I myself started to use on the fly PCM to DSD conversion with foobar2000 and foo_dsd_asio (ASIO proxy) more than 10 years ago. I experienced it as improvement over PCM output to my DAC. Then I switched to HQPlayer version 3, after trialing and recognizing the improvement HQPlayer brings for my ears. Was it a substantial difference? There is no way to measure it, since it is all about subjective opinions. I'm just not a person who pays hundreds of EURos for nothing. For me it was a substantial difference. Since that time many new and improved HQPlayer filters and modulators were added into HQPlayer.
I tried also JRiver MC and also some offline PCM to DSD conversion tools - from Tascam, Korg, SoX DSD extension by Mans Rullgard, I don't remember all. I found nothing on HQPlayer level. For my ears the best ones among them were the foobar extension and SoX DSD extension, Tascam one being the worst.
About Roon, many HQPlayer users are using Roon for library management and playback control, since
HQPlayer is officially supported by Roon. Why would people paying for Roon yet buy HQPlayer license if there would be no substantial difference in sound? HQPlayer trial is fully sufficient to try it with Roon.
Of course, everybody is welcome to compare more solutions and express his own opinion. It can be one of different opinions than most of people have, but that's fine. Perceiving music is a subjective thing where we don't need to agree. No absolute truth exists in this area and I fully recognize this fact. What I complain is your generalization 'nobody said that'.