Be aware that this doesn't always happen correctly (having two people with different credit cards on the same room). My friend and I shared a room, and although we were assured that our charges would be kept separate, all of our charges (including mine) went to my friend's credit card. We were even able to set up our own separate PIN numbers, but it didn't work right. Luckily, I checked on Day Two of our trip, before we reached the $500 charging threshold for AoA (since they would have automatically charged my friend's card).
I spent some time at the front desk of AoA getting our charges separated, and was once again told our charges would stay separate going forward. Again, our charges all went to my friend's card. Spent more time getting them separated, and finally gave up using my band for charging. Such a pain!
So, you might get lucky and have it work correctly, but it's a good idea to stop by the front desk to double-check periodically.