You don't have to wait for the RO2 SDK. The version used for RO uses most of the same principles, so if you learn it, you'll be able to hit the ground running when the new SDK is released sometime in 2012.
Get the RO SDK, which you can still download free if you have RO -- look in Steam --> Tools and scroll down the list til you see Red Orchestra SDK Beta. (If you don't have the original Red Orchestra, go ahead and spend the 4.99, it is well worth it).
Open the maps in RO and look how they're built. Open one, save it as PompMap.rom and mess around with it. Have fun. You cannot break it, so take risks (but save backups often!).
Study the RO modding forums at
[URL]http://forums.tripwireinteractive.com/forumdisplay.php?f=14[/URL]
Nearly every question that will occur to you has already been asked and answered there.
Get this .pdf that will tell you everything you need to know to get started and walk you through the process of making your first simple maps.
[URL]http://www.redorchestragame.com/downloads/manuals/RedOrchestraSDKManual.pdf[/URL]
If you do somehow manage to screw up your game or SDK files, there's a simple fix --
In your Steam games list
1. Open the Properties window for the game
2. Hit the Local Files tab, click
VERIFY INTEGRITY OF GAME CACHE
After this the game should be ready to play and you can go back to messing around with your map.