If I want to setup a Headless Linux Ubuntu Server with Roon. Do I need Roon Server or Roon Bridge? The website says you can run both on the same, but why run both if they function the same? I guess I am confused with the purpose of both as the website isn't really clear. What I want to do is setup a media server and have it serve media with multiple devices like a phone, network streamer, DAP, receiver, ipad, etc with maybe the app or web interface.
You need one Roon Server. If you already have one, you don’t need another one. The purpose of Bridge is to turn any computer into a Roon endpoint (i.e. output device)
No, The Roon system (server) gets configured “internally” through Roon (the client app). If you want a WebUI to manage your headless Linux system then look into your distributions package management, maybe there’s already one (Cockpit and Webmin are popular candidates) included for easy installation.
PS: Ubuntu should have Cockpit in its repositories.
ARC is for mobile use and does not have any ability to configure the RoonServer.
You need to run the client app on a PC or tablet for full options, or Roon Remote (which is a different program than ARC) on a phone. But, note, that not all options are available on the phone app