Not quite sure what you are asking.
Are you asking if your bounceback code is good for 2 additional rooms? I'm pretty sure the answer to that is No, but it wouldn't hurt to ask Reservations if it is possible. The worst they can do is say No, and if you don't try, the answer is surely No.
Are you asking if another room code that you received could be used for 2 rooms other than the one you are in, since you are using a bounceback code? I don't know the answer to this, but I'd bet the CM on the reservation line could help figure it out. If it is a code specifically for you, you would probably have to rent the first room in your name, and have the second room be in the name of another member of your party. It would end up that you have your bounceback room, and room #1 on your code, and then someone else would have room #3.
But actually, I'm not entirely sure I got your question right!