Rockets are only used like an SBR. They do not attack land units.
You can steal pieces from whichever games you like if you feel you need more pieces and don’t want to go thru Hasboro to get more. Just don’t forget to put them back or keep all your games in one container. You wouldn’t want to grab a game to go to a friend’s house and find that all your pieces are in another set. They are your sets do as you want. :-)
I keep meaning to get a container and combine all my games into one box. I don’t think the Pacific Japan pieces will look very good on the Revised board but I often need more ARM and INF.