So, no music server is needed? Sorry, I'm illiterate when it comes to Roon.
Run Roon on your Mac/PC (assuming it meets the very modest minimum requirements). Make sure the Mac/PC is connected to the network via Cat 5/6. Then, run another Cat 5/6 cable to the back of the QX-5 Twenty. Control the QX-5 Twenty with Roon on your iPad. Done.
Let me know if you have any questions.