If you want to update your drum sounds someday in the future, a sampler or a keyboard that has expansion cards is a must. After a quick look at the RS-5 and 9, I don't see any expansion slots in the spec sheet. This is a major red flag.
Roland bills the RS series as performance keyboards (read: "not the keyboard that you want for serious studio work"). Since the sounds are based on some of the XV sounds, it will probably sound great "right now". But in 2-5 years, the sounds are going to be dated. At least with an expansion slot you could buy new drum sounds. Plus, I don't know a keyboard or module yet that has all of the drums that I want to play in the basic setup.
If I were buying, I would leave the RS in the store and get a sampler or a keyboard/module that had expansion slots. If you like the Roland soundset, perhaps you should think of
the XV3080 or 5080 with a Studiologic controller (or some other brand of controller). If money is an issue, even the Roland JV 1010 or
the XV5050 has one and two expansion slots, respectively.
Bottom line: If you want current drums you have to get a sampler. If you don't have a sampler, you need a keyboard or module that has expansion capabilities. Anything else is a serious compromise.
E