The official list from Roon Labs is about partners participating in partner programs (Roon Ready / Roon Tested). There is currently no partner program for Roon Servers AFAIK. Read also:
We killed the “Roon Core” partner program years ago. It was a soft program, with no certifications or endorsements. We basically allowed some manufacturers to redistribute the RoonServer software for Linux on their machines.
For years now, this granting of access to redistribute RoonServer has been denied to all newly inquiring manufacturers. It was nothing but pain for our support team, and while many end-users have been happy, our largest group of complaints also come from buyers of third-party servers. Innuos and a handful of others are from before the killing of the program.
One exception to this was Merging Technologies, which ships a customized version of Roon OS (they add Ravenna support) on their NADAC+PLAYER. Those machines are stable, fast, sound great.