We are preparing for our production of "Annie" and are wanting to have a movable, rotating stage for two of the scenes. I have never built one, and being a small childrens theater, neither have any of our volunteers. The floor space needs to be approx. 12x12 with the ability to hold up to 1000 lbs. Any input would be helpful.

We produced Annie this past season and used four rotating rounds each eight feet across.  Over the years we have found it works best to mount casters upside down on the floor so the wheels point up.  The reason we put the wheels on the floor facing up instead of on the round facing down is that it reduces the wear on the stage surface.  We used 16 wheels per rotating platform set in two circle patterns.  The platform needs a solid anchor point in the center.  For this we used cast iron flange and pipe.  Make sure you secure the anchor point realy well before you build on the round.  Someone (me) didnt do that with our rounds and we had to use rolling automotive jacks and jack stands to get under the round to reattatch them with the set already built on top. 

I agree that mounting the wheels to the deck instead of the platform will protect the stage surface, we still have caster marks in our deck from our first production of noises off from over 15 years ago. dont scrimp on the casters either, my first wagon show we grabbed whatever we could find and opening night they all blew out. had to drag thump it for every set change which was not pretty. "you know what you call a wagon without wheels? A drag