For stock RO .u files you can use the SDK editor as worluk suggests using the export command.
You can also decompile .u custom files; I've done it a number of times.
Using a custom player class named "WSSCamo44.u" as the example in this case here, go to your DOS prompt and then cd to your Red Orchestra System folder. It should look something like this:
C:\program files\steam\steamapps\common\red orchestra\system\
then type this in on the same line, right after "\system\"
ucc batchexport WSSCamo44.u class .uc c:\Decompiled Classes\WSSCamo44\Classes
"c:\Decompiled Classes\WSSCamo44\Classes" indicates a folder I set up on my C drive to receive the decompiled class files.
Hope this helps!
You can export most texture and sound files out of their respective .utx and .uax packages by using the SDK editor.
(Disclaimer: I cannot be held responsible for you jacking up your red orchestra system files
)
And this thread should probably be moved to the "Coding" section...