You need to pay to upgrade. Just a note that SPG Gold upgrades to RBC do not include any amenities including, I was just told by the front desk, use of the pool and towels (you're given two towel cards, and you are expected to walk all the way back to the main building and use the towels and pool there), and of course no breakfast or happy hour. They are giving out bracelets for Plats and paid rooms in the RBC to keep out interlopers apparently. For $90 a night I can get the amenities with the upgrade, but as it stands the upgrade is for the room only -- doesn't seem worth it if you can only use the room. Final analysis, contact the hotel in advance for a paid (cash) upgrade.