Marcelo Bosch comes in for centre Gonzalo Tiesi, who is out of the tournament with a knee injury, while Lucas Gonzalez Amorosino will start at fullback.
That allows Martin Rodriguez to move to centre and Santiago Fernandez to switch from midfield to flyhalf in place of injured captain Felipe Contepomi.
Number eight Juan Martin Fernandez Lobbe will captain the side for the seventh time, while hooker Mario Ledesma will set a national record 15th World Cup appearance, moving ahead of Contepomi and former scrumhalf Agustin Pichot.
With the pivotal September 25 game against Scotland looming in the background, Argentina might have been expected to rest some key players but Romania's impressive display against the Scots and the Pumas' own limited game time together led to them to opt for continuity.
"Romania have a really good pack and a good defence, we saw that against Scotland," Lobbe said.
"We'll have the same approach -- a great defence, keep our tackling low, and try to stop them at lineouts and rolling mauls.
"We will do the same as we always do. Everything we do is for the team and 110 percent is the only option. We will put our bodies on the line and our hearts on the pitch."
Lobbe said Argentina were still stinging from losing to England, having dominated for long periods but failing to make that tell by missing six of their nine penalties.
"We managed to control them but they showed a great confidence and resolution to be patient and wait for that little mistake, which unfortunately we made," he said in reference to the only try of the match scored by replacement scrumhalf Ben Youngs 15 minutes from the end.
"We had a big, big chance. I think England did well, but it was us who lost it."
Lucas Borges has flown in to join the squad in place of Tiesi while the team management were unable to predict a time scale for the return of Contepomi, who has bruised ribs.
"He will obviously be missed, he's our star, the leader and the captain who can make a difference," Lobbe said.
"But we believe we have a strong squad and can make it, so we won't miss him too badly."