All the RO2 music is encoded in the game files in OGG format.
You need to use a tool (freely downloadable online) to convert the Unreal engine data files to ogg files, which can then be played in your favorite media player.
I did this, and they sound great. They make for perfect background music when I am doing other things than playing the game.
Side note:
From a legal perspective I would only do this if you actually own the game, and not spread the files around.