So today i started my weekend with again trying to get roon working (:
i decided to start completely fresh including a new LXC with roon server on ubuntu.
(aside from the official documentation being outdated it looks like it is working well)
https://help.roonlabs.com/portal/en/kb/articles/linux-install#Roon_Server_x86_64
easy installer link is http and fails (needs to be https)
curl is not on every system and needs to be installed beforehand as well as lbzip2
So i continued with another try of bottles (i like programs being contained like in a flatpak bottle:)
which worked so far like the other times i tried. ( Roon 2.0 and Linux (Wine) .. is 32bit needed? [answer: no, wine supports 64bit] - #117 by Tristan_Harward )
the new problem is that the login is now permanently a web-redirect? (wth ???)
so my Question is: how am i supposed to log into my roon?
//EDIT1 managed to mount a network share and put a backup of an old roon server into it.
it was possible to connect to the server and restore the backup successful sadly login is still not possible 
//EDIT2 Trouble Logging Into Roon App Without Web Redirect (ref#H7ETR0) helped out alot. As i understand its a one off thing (still think its bad design tho).
→ tried to install a browser into the same bottle but that got messy. Luckily i have an old phone which i used to hook into the same vlan as roon (be aware the roon app does not like old android versions [which would be ok if it wasnt nessesary for the login ^^])