American driver Robby Gordon was third after the 10th stage but he had a series of mechanical breakdowns in his Hummer and dropped out of contention, almost 2 hours behind Peterhansel in the stage.
In motorbikes, Cyril Despres of France won the stage to stretch his small lead over defending champion Marc Coma of Spain.
The Dakar Rally ends Sunday in the Peruvian capital of Lima.
Peterhansel won the 478-kilometer (297-mile) special stage in 3 hours, 56 minutes, 53 seconds. Roma was 3:44 behind and teammate Ricardo Leal Dos Santos of Portugal was third, 8:56 off the pace.
Peterhansel leads Roma by 22:49 overall and is 1:11:01 ahead of third-place Giniel Devilliers of South Africa.
Gordon is fourth overall, 2:10:31 behind.
"The only way we'll win is if the other guys have problems," Gordon said. "But you know, that's the Dakar. You fight, fight, fight and hopefully it doesn't get you, but today it just got us." Despres finished the special stage — 534 kilometers (332 miles) for bikes — in 4:03:37. He was 1:39 ahead of KTM teammate Gerard Farres Guell and 2:01 in front of another KTM rider, Coma.
In the overall, Coma trails by only 2:22. Hedler Rodrigues of Portugal 1:08:40 behind in third place.
