Arrive in Rotterdam, train to Hague early afternoon and stay for one night.
Train back to Rotterdam, book in hotel and then train to Amsterdam for the afternoon, Return to Rotterdam.
The next morning and afternoon in Rotterdam.
Two nights in Rotterdam and spend the same time in the above places: Rotterdam for afternoon on day of arrival. Hague, Amsterdam the next whole day. Rotterdam on the last morning.
Stay in Rotterdam for both nights, stay in Rotterdam first afternoon and explore; use the whole day for a trip to Dusseldorf via Utrecht station. Amsterdam early on the last day. Then back to Rotterdam and home.
If you could let me know which would be best, it'd be greatly appreciated