@brian recently commented about Roon’s performance workload:
Either of the computers will easily run Roon. My suspicion is that any discernible difference in performance might only become apparent with a pretty large library.
I’d be inclined to let HQP have all the room it wants and keep Roon on the quad i7. You’ll get some increased network traffic, but I would not think that would be a factor for gigabit Ethernet.