You need to reinstall Roon because you deleted parts of it.
If you try to reinstall, the it tells you to quit all instances of Roon because the Roon Server runs as a separate process from the graphical interface.
- Quit the graphical interface by closing its window.-
- Quit the Roon Server by right-clicking the Roon icon in the notification area on the task bar, then click Quit:
Then start the installer again.