Am I not understanding something with that support?
Each one of those servers has a different protocol to access it. To make mt-daapd/firefly be able to browse by directory would require changing the protocol (doable), but if the protocol changes, it would have to be changed on the client, too.
Either that, or I could implement the same kind of server protocol that twonky et. al. do — upnp. that’s on my roadmap, but upnp is kind of suckish (imho), and I like the speed of rsp, so I’d prefer to do it that way.
So the “right” way would require changes on the roku side, and the “wrong” way isn’t on my near-term roadmap.