Is there a way to rearrange the order of the items in the queue?
If, as I fear, there isn’t then I think there should be, simply by dragging them to where you want them. I tried that, and it just scrolled the whole queue.
The queue is a relatively simple feature that JRiver does much better, both in its usefully wide range of options for where new items are added in the queue (I have previously done a feature request in that connection), and also ease of rearrangement when your listening journey changes direction mid-queue.
I can’t ever imagine going back to JRiver for music playback, because of the sophisticated stuff that Roon does increasingly well, and which JRiver never will. (Nothing to do with having paid the lifetime sub already, oh no. 
). But it is frustrating that Roon’s functionality often seems to lag on the simpler stuff like this.