IHH,
I can't answer for Rosie, but I'll add my few "notes": I'm a flutist (flautist, if you want to be snooty), a pianist, play all of the recorders, and sing as a mezzo-soprano.

I've been really lucky - my RSD is in my leg, so I still get to play, although my musical theater career has gone out the window.

Seriously, though - I have at the least had the same sort of problem with walking. After 8 years of RSD, I can't tell you anything that will make you jump for joy, but I have learned that the absolute most important part of your treatment is keeping a positive attitude. Really - it's so important to focus on the things you are still able to do, and on each new stride you make. That sounds like a bunch of platitudes, I know. I'm sorry. Have you thought about trying to redirect your musical energies? Do you sing, for example? Have you thought about trying your hand at composition? Composition is great because it's a wonderful source of expression - I love it.

Nice to meet other musicians! And you are, even if you're not playing at the moment.