We definitely work on those keys at the camp. It's OK to chop chords a lot. People will think you're tasteful! You can also roll smoothly while following the chord changes, which is often the best thing to do for backup. When it's time to solo, do the same principle as you do in G: Follow the chords and follow the melody, trying to put it into rolls. Finding melodies in an unfamiliar key is slow at first, but like learning any "new neighborhood", you start remembering where things are. As in G, the melody notes, especially the main ones, that fall on downbeats, are usually found within the chord that's happening at any point. For high notes that can be found on the first string, it's usually easier to locate the same notes three frets higher on the second string, which makes them easier to work into rolls. Also, you'll find some useful left hand formats that you can improvise out of, and those help in a jamming situation. That's the best I can describe it in a short space, and then it's up to the person to do the practicing.
At banjo camp we dive right into this sort of thing, by picking a typical song played in a key like D, and working through it. For a head start on this kind of material before coming to camp, check out my videos "Branching Out on the Banjo".