Is there a Roon ready DAC with an instrument (guitar) input and some line outs such as the Steinberg UR22mkII?
Not exactly RoonReady, but I’m streaming via ethernet from a Roon bridge to a Metric Halo LIO-8 3D performing DAC, RIAA equalisation, active crossover and preamp duties. It has two DI inputs on the front panel - e.g., for guitar, and multiple digital and analog, including preamps for gain if needed, via DB25 inputs on the rear. Incredibly flexible piece of gear. Can’t speak highly enough of Metric Halo, either - with whom I have no connection, other than as a very happy customer.
What is your purpose is it to play along?
Just get a guitar amp and play along or get a simple analog mixer like a Yamaha MG10 (with limiter functions) to take a microphone feed off your guitar amp. Guitar is too clean and high dynamic range to just straight combine with produced music. Guitars love tubes too!