I've got a rose gold watch and I have, no joke, 26 bands for it (and counting). What can I say --- I love accessorizing. I also happen to think that most bands go fine with the rose gold watch, but I'm not a super matchy-matchy person. How does your wife feel about mixing the rose gold with silver or gold metal features, for example?
My favorite sport colors with my rose gold (so far) are the OEM lavender, the antique white, and the stone. I love the black milanese loop band with it as well, although I think it also looks good with the silver link and milanese loops as long as you don't mind mixing metals. I also love it with most leathers --- I am fond of turqoise, light tan, and white, and hope to get a medium brown soon. My least favorite bands with it are a third-party walnut sport (which is a darker tan than Apple's version), the black sport, and a dark blue sport. I also think the orange and red sports clash a little bit since they are such warm colors. I still wear them from time to time though.
I uploaded most of the photos I've taken of the watch with various bands here:
https://goo.gl/photos/Q5nE9mW3bhA8qVdM6. I'll try to add to that album as time goes on.
tl;dr: muted neutral sport band colors, any shade of brown leather, or the black milanese.