Are there any instructional materials out there on this subject?
Yes - your record/cd/mp3 collection. :-)
And that's not at all intended to be a flip answer.
This is an area which I believe can ultimately only be figured out on an individual player basis through as thorough of an exploration of the recorded archives as possible. Only with a good handle on "how has it been done before?" can a player, when confronted with one of thousands of musical scenarios, come up with the "best" way to deal with each one.
For me, studying this amounted to A LOT of playing with records - sometimes learning note-for-note what the player on the record played, though probably most often simply finding the closest paraphrase of what he played that I could muster. Then after that, I would also start to try different solutions - different fills, different transitions, different from the record (maybe only slightly, but sometimes dramatically different) - all in the quest of figuring out why the drummer might have chose to do what he did, and what the other possibilities might be instead. Always keeping open to the fact that the notes on the record might not have even been the best ones (though of course often they were) - so lot of playing, analyzing, playing, analyzing...all at the same time.
Another great exercise for all of this IMO was to take a snippet of some kind of transition - like setting up a transition to a section that starts by accenting/pushing the & of 4 for example. Anyway the exercise would be to repeat it over and over starting with the simplest approach possible, and with each repeat getting incrementally more complex - and seeing how many repeats I could do without ever back tracking (getting simpler) - a real exercise in restraint... jump ahead too soon and you'll run out of choices quickly.
Another variation of this would be to simply repeat the short transition area and see how many different approaches you can come up with on the fly. If I couldn't come up with many - then that was my cue to learn some more "stuff" from some more records.
The idea here is, in every situation, to have as many arrows in your quiver as possible. This way, while actually playing, your focus can be all about listening to the music and discerning what would best serve it or at least serve the effect you're are wanting to have. Then as you decide, it is just a matter of pulling out and letting fly with that specific arrow.
And I don't see anyway of digging in, figuring it out and cataloging it yourself. Any kind of book on fills is either going to cover very little ground or it's going to leave out way too much of the music context. And I believe, it's cataloging each fill, variation and device with it's various musical contexts that is important here. Not just learning the fills, variations and devices themselves.
And the end result of all this really goes a long way in define each player's specific personal style - because we are each going to catalog and prioritize each of these things a bit, or a lot differently from each other.
Hope that helps.