I've had Roon for over a year now and I don't think I could use anything else. Yes, the price is a bit of a sting at the outset but when you see just how nice it is to use, and how much heavy development work is going into it, it feels worth every penny.
Getting it up and running on the Pi isn't quite as simple as just writing an SD card and plugging it in but there's a comprehensive guide on getting RoonBridge going here:
http://kb.roonlabs.com/LinuxInstall and once you've done it, you don't need to think about it again. Any software updates are applied automatically and in use, you just switch on the Pi, let it see your Roon server running on your PC/Mac/NAS and take control of everything with your phone/tablet/PC running the Roon Remote software.