Santiago Fernandez and Juan Manuel Leguizamon crossed in the first 10 minutes and further scores before the half-hour mark from Juan Figallo and Lucas Gonzalez Amorosino took the Pumas out of sight, despite Ionel Cazan's swift reply.
Romania defended stoutly throughout much of the second half but Juan Jose Imhoff and Gonzalo Fessia added further scores to give the scoreline an ultimately one-sided look.
Although the match had been billed as a battle between two powerful packs, the Pumas confounded expectations and thrillingly chose to run the ball at almost every opportunity.
Fernandez, starting at fly-half instead of injured captain Felipe Contepomi, sliced through some slack defending in the fifth minute for a try near the posts which Martin Rodriguez converted.
And just four minutes later flanker Leguizamon collected a pass on the 22 before powering over the line.
Romania were awarded a penalty near the Argentinian line after 13 minutes but opted for a kick at goal, Tiberius Ionut Dimofte successfully landing the penalty.
But prop Figallo registered Argentina's third try on 20 minutes after a quick tapped penalty by scrum-half Nicolas Vergallo.
Man of the match Amorosino then showcased his evasive running skills to touch down under the posts before Romania proved they could run the ball as well, setting up winger Cazan to score in the corner on 32 minutes.
As Argentina continued to pile on the pressure in the second half, prop Mihaita Alexandru Lazar was sin-binned for stifling another attack, but that simply delayed the inevitable.
Imhoff scored under the posts just seconds before Lazar's return and Argentina rounded off an entertaining performance in style, going the length of the field for Fessia to score after Romania had spilled the ball near the Pumas' line.
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