Crack them open with Vecingetorix`s tool. Here`s a guide too:
IIRC there is a sample pack that Vecingetorix has included so you can get an idea on how to repack things. But, you might want to take a look at this thing for repacking. It really makes the life easier.
If the link in the first post doesn`t work, see that there is a dl link in his sig. Or search for it on the dl section of twc. I think it is also uploaded there.
Do you mean .rsd ? the ones that control how the UI elements are displayed - if so I don't think you can directly, you can view in text / hex editor but I'm not sure anyone managed to change them. Alpaca cracked the .sd files for M2TW which are similar thing so it might be worth looking at how that was done.
Otherwise if you meant .rwm (the sort of save of map information in campaign folder) then again I don't think you can do anything useful with it.
.....waits to be embarrassed when you explain what .rmd actually is.....