Mini driver Roma claimed his second stage victory of the 2013 edition on the fast route from Tucuman to Cordoba - his 13th career win.
The Spaniard crossed the line 4:11 ahead of Peterhansel in second, with Argentine Orlando Terranova 6:54 back in third.
Nasser Al-Attiyah suffered a nightmare stage, the Qatari having to stop several times to effectively end his hopes.
Peterhansel extended his lead at the top of the standings to 49:31 with Giniel de Villiers in second ahead of Leonid Novitskiy in third.
"It was a long special requiring great handling skills," Peterhansel said. "Towards the end you start to get tired and you're less lucid, for example on trails with lots of stones.
"We had to stay focused and avoid making mistakes, it's very easy to have a puncture or break a wheel. So we maintained a cautious but steady pace.
"On courses like this, it's not surprising that the buggies run into trouble. We could have gained even more time, but we would have had to take risks.
"It's getting closer, but there are still a few long stages left which favour the buggies. We need to take time whenever we can, because we can always make mistakes in Fiambalá or on the dunes of Copiapó."
- Sports & Recreation