The 34-year-old Welsh driver was gifted the lead on Friday when local favourite Rovanpera, 22, his Toyota teammate, was forced to retire after crashing.
After taking the closing power stage Evans came home 39.1sec clear of second-placed Thierry Neuville of Hyundai.
Evans moved to within 25 points of championship leader Rovanpera with four rounds of the season remaining.
"It's been a pretty good weekend," said Evans, 34, after his seventh career win and second this season after Croatia in April.
"Of course we're sorry for the loss of Kalle at the start of the rally but after that it's been really fantastic to drive this car - it's such a joy to be behind the wheel of on these roads and we're really happy with this one.
"It's been a fantastic atmosphere and great to have the support behind us. Of course, in terms of the championship it's also not bad and we close the gap."
Neuville finished nearly a minute ahead of Japan's Takamoto Katsuta to stay third in the world championship standings.
Only five cars in the WRC1 category finished the race on slippery and muddy roads.
As well as Rovanpera, Estonian Ott Tanak, the 2019 world champion, was also forced to retire with mechanical problems on his M-Sport/Ford.
Finland's Esapekka Lappi of Hyundai crashed out on Friday.
The next rally is in Greece next month.
