Rovanpera beat teammate Elfyn Evans by 23.4 seconds in the Concepcion-based rally to secure the Finn's fourth win of what is only a part-time season for the reigning double-world champion.
The win, in the last gravel round of the season, was the 15th of Rovanpera's career.
Hyundai's Ott Tanak completed the podium, 20.5 seconds behind Evans, with Neuville fourth.
Neuville now has 207 points to Tanak's 178 with Toyota's Sebastien Ogier on 166 and Evans on 161 with two rounds remaining.
The Belgian could clinch the title at next month's Central European rally on asphalt roads in Germany, Czech Republic and Austria.
"We knew it would be a challenging weekend, we did not have the performance package this weekend," said Neuville. "It was visible to everybody that we could not fight the Toyotas.
"We have two more events this year, we are looking forward for them to come and I am happy the gravel is over."
Ogier's hopes of a record-equalling ninth title receded, despite securing maximum Sunday points after he retired from Saturday's penultimate leg with suspension damage.
Toyota closed the gap to leaders Hyundai in the manufacturers' standings to 17 points with everything still to play for.
