Unlock Secret Camouflage room:
Beat both New Game types.
Unlock Banana Camouflage:
Set the top time record in all the Snake vs. Monkey stages.
Unlock DPM Camouflage:
Beat Special Duel mode on Disc 2.
Green Face Paint:
Beat Normal Duel mode on Disc 2.
Reiko and Dixie:
Rack up 50 hours of online play to unlock Reiko and Dixie from Rumble Roses.
Demo Theater/Secret Theatre:
Simply save your game during disc 1 to unlock the Demo theatre on disc 1 and the Secret theatre on disc 2.
Thanks to Revolution Readers goldenman and STEV-1!