Rovanpera will secure the championship in the season's penultimate round if he matches or beats teammate Elfyn Evans' points haul.
Evans was running in third place but 47.2 seconds off the Finn's pace after the day's six wet and slippery asphalt stages in the Czech Republic.
Rovanpera won all three of the morning stages, taking advantage of being first on the roads with less mud to deal with, and he won one more in the afternoon.
"It has been super tricky today," said Rovanpera.
"Luckily, the weather was on our side for once with the starting position. It was good to be the first car on the road. We can be happy with our day."
Neuville had led after Thursday's opening two stages but dropped to third before getting back ahead of Evans on the day's closing stage.
M-Sport Ford's Ott Tanak was in fourth place with Toyota's Takamoto Katsuta fifth and France's eight times world champion Sebastian Ogier in sixth place, also for Toyota.
Hyundai's Esapekka Lappi crashed heavily on the fifth stage, without injury.
Saturday features two stages in Austria before moving into Germany.
