From my personal experience, the answer to that question is both. The folio for the room will be the total amount spent between any charges made for that room #. But it will also list by name who's charge it was so you could add it up & divide it out yourselves. But that may have been because of my particular situation on my last trip in March: When I checked in at the counter, I had the CM swipe one CC for my MB & one for my roommates so that the room accounts would be separate. Unfortunately, all of the charges went onto my CC in the end & we had to scramble to get the $ into the account. So, if you do have the CM at check in scan different CCs for your MBs, keep an eye on it as you go to make sure it's separating the charges.
Had it worked out the way we planned, I'm not sure if we would've received separate folios for the room we were in or it would've just broken down the charges under our names separately.