Yes. It will be filled with few cans of beer & soda, small bottles of liqour & wines, etc and some goodies. There should be a price list on the dressing table or ask your cabin steward for one.
If you don't want any of the stuff in the fridge and want to put your own stuff in, then ask the steward to remove it.
Enjoy the Rotterdam - we've had many great cruises on her.