We just returned from the Rotterdam. Upon boarding we were directed to take the elevator to the Lido deck, and check our carry-on luggage by the Lido pool. We received a claim ticket and were told to procede to the Lido Cafe for lunch. About 1 or 1:30PM they made an announcement that cabins were ready, and we claimed our carry on luggage and went to our cabin. No one escorted us, but If you arrive at a later time they will escort you directly to your cabin.
You may also stay in your cabin at debarkation until your color is called.
It was an easy and painless procedure and very well organized, I thought.