The Diamond Force / guarantee is for one room. Even rooms not booked with Diamond Force often have the following language:

"A maximum of one room per night at a specific hotel may be booked as part of the Diamond Guaranteed Reservations benefit. Additional rooms booked via this benefit at the same hotel for the same date(s) may be cancelled by the hotel and accommodations denied without any liability for cancelled rooms."

How that will work for three separate rooms I don't know, but it sounds chancy to me.