Didn't notice this till I tried removing my custom roon user from the one I was testing with. There's not a 'groups' option for users, only group (primary group) and extraGroups. Use these.
(#68337)
DynamicUser currently breaks the backup functionality provided by roon,
as the roon server cannot write to non-canonical directories and the
recycled UIDs/GIDs would make managing permissions for the directory
impossible. On top of that, it would break the ability to manage the
local music library files (as it would not be able to delete them).
