They aren't really designed to be taken apart, but if you bend a tab back on the ends, you could get the rollers out and the two parts of the rails apart. I'm not sure I'd recommend that though, as you may never get them back together.
I'd be more inclined to soak the whole assembly in Evaporust, which will get the rust off, then rinse them in water and dry and spray some light oil on them.
If you do decide to disassemble them, post up some pics.
