A bug in iOS is certainly a possibility, but not the first possibility an experienced developer would consider. To identify an OS bug we’d need to rule out a bug in the app through focused testing. Roon might have done that investigation, but without asking we can’t know.
I’d recommend posting this to the support board with as much detail as you can provide about your hardware, OS versions, and if any patterns have been noticed when you get a hang (is it always on the queue screen, the album screen, after a certain length of usage, etc.