Hi and Welcome to FRF.
It is always helpful to provide which model number your Rockwood is.
If it's a actual 12v only fridge, it should be connected straight to the battery. An inverter inverts 12v DC power to 120v AC power.
A residential fridge would be powered through an inverter, not a 12v only fridge.
Did you receive a poor PDI/walk-through from the dealer?
Dan-Retired California Firefighter/EMT
and Zoe the Wonder Dog(R.I.P.)
2016 PrimeTime TracerAIR 255, pushing a 2014 Ford F150 SCREW XTR 4x4 3.5 Ecoboost w/Max Tow Package
4pt Equal-i-zer WDH and 1828lbs of payload capacity