I think you hit the nail on the head Keith; to me Roon sounds as good as the other players when no upsampling or special filtering is used (or at least close enough that I would always choose Roon because of the more attractive UI).
If you do have a high-end system and work with the upsampling and filtering capabilities offered by an Audirvana or an HQ Player so as to fine tune them to get the best result for your system, they do sound better. But that is also why the Roon team is working toward an HQ Player integration. That won’t be for everyone because the degree to which you can finetune HQP also means too much work for many users, but for the perfectionist it will truly offer the best of both worlds when integrated with Roon.