Today I'm working on my latest arrival from Brazil and the initial exploratory roast would make for a pretty interesting training exercise. I have 9 cups, each representing a different potential end point ranging from start of 2nd crack through to a bit beyond what I'd like as a French Roast, and within that, the core characteristics of the coffee are remarkably stable, which makes it a good example of what you can generally expect as coffee gets darker.
Some coffees have distinct cuts where at certain points you get a big, distinct change in cup character, so you have maybe 2-4 categories of general characteristics you can aim for and manipulate the roast within, and those are interesting in their own way, but here it's really all just levels and intensities shifting and deciding what kind of balance you want.
