Goals from Klaas-Jan Huntelaar and Robin van Persie ended Romania's hopes of making the Euro 2008 quarter-finals.
Italy's win over France meant that the Romanians had to beat the Dutch to progress, but they rarely threatened goalkeeper Maarten Stekelenburg.
Huntelaar opened the scoring in the second half when he slotted in Ibrahim Afellay's low cross from the right.
And Van Persie secured table-toppers Netherlands their third win from three when he smashed in from close range.
The Dutch will now play either Russia or Sweden in the last eight and following their first three performances Marco van Basten's team will fancy their chances against any side.
The makeshift starting XI - nine changes made - started tentatively as did Romania, but for very different reasons.
Victor Piturca's men knew a win was required to guarantee their berth in the last eight while the new-look Dutch were fully aware they needed to impress Van Basten.
As a consequence, the opening moments of the match provided few champagne moments.
However, there was goalmouth action, albeit of the half-chance variety.
Romania's top marksman Adrian Mutu came close on two occasions after creating the openings himself.
His first effort resulted from a clever twist and turn on the left-edge of the six-yard area that was deflected wide by the boot of Wilfred Bouma.
Mutu's second effort was more spectacular - a shot from 25 yards that flew two feet wide of Stekelenburg's right-hand upright.
They should have hit the target just before the break when Paul Codrea fired over from 12 yards following great work by full-back Razvan Rat down the left.
The Dutch went even closer. Demy de Zeeuw threaded the ball to Huntelaar who in turn flicked the ball to Arjen Robben.
However, the Real Madrid star was perhaps a little too nonchalant, poking his shot a yard past Bogdan Lobont's right-hand post.
By this point it appeared that coach Piturca knew Italy had taken the lead against France and that his team required nothing less than a win.
If the 11 on the pitch did not know the scoreline in Zurich during the first half then they were surely aware of it by the restart.
But instead of throwing caution to the wind the Romanians seemed more cautious and anxious - for that, they paid the price.
The men in white were given a warning by Van Persie whose turn and shot from eight yards was brilliantly saved low by Lobont.
But within 10 minutes the Dutch punished their opponents when Afellay's low ball from the right was calmly converted by Ajax forward Huntelaar.
Foward Daniel Niculae was brought on for Marius Niculae in the hope he would reinvigorate the dispirited Romanians - but there was to be no Turkey-style comeback.
On the other hand, the Dutch looked more comfortable as the game wore on and Van Persie wrapped things up with the vicious strike into the roof of Lobont's net from six yards.
Netherlands: Stekelenburg, Boulahrouz (Melchiot 58), Heitinga, Bouma, De Cler, De Zeeuw, Engelaar, Afellay, Van Persie, Robben (Kuyt 62), Huntelaar (Vennegoor of Hesselink 82).
Subs Not Used: Van der Sar, Timmer, Ooijer, Mathijsen,Van Bronckhorst, van Nistelrooy, Sneijder, De Jong, Van der Vaart.
Goals: Huntelaar 54, Van Persie 87.
Romania: Lobont, Contra, Tamas, Ghionea, Rat, Cocis, Codrea (Dica 72), Chivu, Nicolita (Petre 82), Marius Niculae (Daniel Niculae 59), Mutu.
Subs Not Used: Popa, Stancioiu, Marica, Sapunaru, Moti, Cristea, Radu.
Ref: Massimo Busacca (Switzerland).