Klaas Jan Huntelaar, 54, and Robin Van Persie, 87, scored two second-half goals to earn Holland their ninth point of in Group C to finish top, five points above second-placed Italy.
Romania and France will be packing home now after a disappointing campaign.
The Dutch second-string side proved to be too strong for Romania as they dominated the game since the first minute courtesy of some excellent work from Arjen Robben and Van Persie on the flanks.
Robben could have opened the scoring early in the first half but he couldn't beat in-form keeper Bogdan Lobont.
The Dutch had to wait until the 54th minute when Huntelaar struck the opener from close range to put pressure on the Romanians.
Three minute from time, Van Persie fired in the second with a powerful half-volley from 12 yards.
Holland will have to wait for tomorrow to know their quarter final's rival as Sweden and Russia will clash together for the second ticket of group D.