Rovanperä built his initial profile in Finnish domestic competition, winning the small Group A Finnish Rally Championship title in 1995 driving an Opel Astra. After several outings on Rally Finland, his home event in the World Rally Championship, he was recruited by SEAT to drive the SEAT Ibiza Kit Car. In 1998, he won SEAT's third consecutive 2-litre World Rally Championship title, cementing his standing as a top-level competitor in the production-based classes.
Rovanperä moved into the top WRC class in 1999 driving the SEAT Córdoba WRC E2, achieving a third-place finish on his debut in the top category at the Network Q Rally of Great Britain. His performances in the 2-litre category had demonstrated the speed that would carry over once he gained access to World Rally Car machinery.
In 2001, Rovanperä joined Peugeot and immediately made an impact. Driving the Peugeot 206 WRC, he took his first WRC outright win at the Swedish Rally, a loose-surface event that suited his aggressive, committed style. That same year he finished fifth in the overall championship despite missing two rounds, only eight points behind champion Richard Burns. He also won the 2001 Race of Champions individual event at Gran Canaria, claiming the Henri Toivonen Memorial Trophy as Champion of Champions, defeating Armin Schwarz in the final.
The 2002 season was a campaign of contrasts. Rovanperä showed consistent speed on gravel and snow — finishing second in Sweden, second in New Zealand, second in Australia, and second on Safari — but struggled on tarmac, where his allocation between the full Peugeot factory entry and the Bozian privateer team left him with less competitive preparation. He retired in Finland while leading, a significant missed opportunity. He finished seventh in the 2002 championship with 30 points.
Rovanperä continued with Peugeot through 2003 and 2004, competing primarily on loose-surface events given the team's selective programme for him. He added three further WRC podiums across those two seasons, maintaining his reputation on gravel and snow while the team's championship challenge was led by Marcus Grönholm.
When Peugeot restructured its WRC programme, Rovanperä signed with Mitsubishi for a full 2005 season. He finished seventh in the drivers' championship, taking one podium — second place in Australia behind François Duval — in what proved to be Mitsubishi's final full WRC campaign before the manufacturer withdrew from the series.
Following Mitsubishi's departure, Rovanperä drove six events for the semi-works Red Bull Škoda Team during 2006. His best result was a ninth-place finish on the final event of the season in Wales, and that rally marked the end of his top-level WRC career.
After withdrawing from the WRC, Rovanperä competed in the SRC Finnish Rallycross Championship in 2007 and in various historic and classic events. In October 2010, he and co-driver Jouni Närhi won La Carrera Panamericana outright in a 1953 Studebaker, finishing just 12.9 seconds ahead of Michel Jourdain Jr.
Rovanperä's WRC career was defined by his excellence on loose surfaces and his near-miss at the 2001 championship, where he came within reach of the title in only his first full season with factory equipment. His son Kalle, who grew up around the WRC, went on to become one of the sport's youngest world champions, winning back-to-back titles in 2022 and 2023 for Toyota Gazoo Racing.