Thank you @Michael_Juday, for clarifying.
This is expected behavior; when Roon 1.8 was released, Apple also released the audioOS 15 update for HomePod devices. We received reports of issues similar to the one you described in your post.
While we don’t have a timeline on when a solution will be provided, we recommend continuing on with this workaround. I’m sorry that this does not allow for stereo grouping, which is ultimately what you are wanting to complete. 
You can read more about this known issue here: HomePod Grouping