With the change in weather, I've started to turn back towards riding my trainer indoors rather than freeze my nose off outside on my real bike. This has lead me to notice that the chain was not running quite as quietly as I might have liked.
I was pretty sure it wasn't the chainrings or the cassette causing the noise. The chain itself had plenty of life left in it and the derailleurs were well adjusted. That just left the jockey wheels, and given that a new set is about $20, I figured there was no harm in just swapping them out.
So that's exactly what I did.
I haven't given them a spin just yet, but with any luck it should quiet things down nicely. I did notice that the old ones felt a bit more loosey-goosey than the new ones, so hopefully that's a good sign that I'll hear some improvement.