I booked a room for three at a Fairfield hotel, using points. When I arrived, I was told the room could not accomodate a rollaway, per the fire marshal. There were no rooms in town, due to a golf tournament. Cathy at Marriott Rewards Cust Service could do nothing, and suggested that a king bed sleeps 3 people. Never again...
When you make your reservations at Marriott.com and select a hotel at choose dates & room rates, select the rate and you will see room preference and you can selece king or double beds, or rollaway/crib reference. Select rollaway bed and in the uper right is "apply these preferences to all rooms in this" if you have 2 or 3 rooms.
I too have run into the 'no rollaway' issue at many properties,no matter what the brand. Although I usually feel like a second class citizen at Marriott when staying on points, in this case I don't think it is related to that--more a consequence of the minimum square footage per room vs. maximum return dilemma hotels face.
I can select rollaways as a preference, but only sometimes have found in the 'fine print' for individual hotels "no rollaways allowed". Definitely not family friendly traveling when this happens. At Vail, we were finally (it took some talking to several people because I'd called out to confirm the rollaway allowance and apparently was given bad info) offered the use of a twin air mattress, which worked for the kids (teen boys who no way no how were sharing a bed!). Very crowded in the standard room, but it was workable and more importantly alleviated the necessity for one sleeping on the floor or listening to them argue all night :-).