Yes, Rolex developed an alloy that I believe incorporates platinum, so it is supposed to be resistant to fading. However, I've already seen on a few Rolex forums, that there are instances where it has faded to yellow.
As for preferring one brand's rose gold to another, yes there are different compositions of alloys using different amounts of copper and other metals. There is actually a color scale for gold. Yellow gold is 3N, a very light rose gold is 4N, a deeper rose colored gold is 5N, and then I believe at 6N you reach what is called red gold.
Very interesting. Thanks for the information.