Why don't you check for yourself - HQPlayer has 30min trial, and after that you just restart the app to continue listening. Plenty of time to evaluate.
Also, your sentence "actually compared Roon vs HQPlayer or using HQPlayer exclusively" doesn't make sense. HQP works WITH Roon, as addon, and does upsampling, even though Roon has its own upsampling DSP, but HQP is much better. So those 2 apps can't be compared directly.
Sure, HQP can also be a player, but its not really its selling point, it can't be compared to Roon, not even close as a player or music catalog.
Benefits of HQP solely depend on your system, what kind of DAC you have and will it benefit from the external upsampling, does it prefer DSD or PCM, do you have powerful enough computer for DSD, whats the resolution and transparency of the rest of the system... So, you just have to test it your self, opinions about HQP setup here are very individual and will be very different from what you'll hear.