I wouldn't run without antifreeze. One of the perks of antifreeze is that it raises the boiling point of the water. If your thermostat is set to open at 220* (not sure what they are on the Rocket, some cars open at that temp) you will run the risk of boiling the coolant. I know its supposed to be a sealed, pressurized system; and that the pressure adds to the boiling point also. But why chance it?
If you want to run the additive, run it and the antifreeze. You'll feel safer and with the anti-corrosion pack in the coolant your engine will feel better too.