Roaldseth, who started for the Molde og Omegn IF , made her first international appearance at the 1996 Nordic Junior World Ski Championships in Asiago . There she took 33rd place over 15 km freestyle and fourth place over 5 km classic. The following year she won the bronze medal with the relay at the Nordic Junior World Ski Championships in Canmore . In addition, she took 28th place over 15 km freestyle and eighth place over 5 km classic. In March 1997 she made her debut in Oslo in the World Cup and achieved 12th place with the relay. In January 1999 in Valkeakoski and in January 2000 in Nybygda she won her first classic wins in the Continental Cup each over 5 km . In the 1999/2000 season she made it into the points eleven times in the World Cup. She achieved her best individual result with fourth place in the sprint in Engelberg and her best overall results with 28th place in the overall world cup and tenth place in the sprint world cup. In addition, she was third with the relay in Davos . At the Nordic World Ski Championships in 2001 in Lahti , she ran on 18th place over 10 km classic and 15th over 15 km classic. In the 2002/03 season she won with seven places in the points, 33rd place in the overall World Cup. At the season highlight, the Nordic World Ski Championships 2003 in Val di Fiemme , she finished 31st in the 15 km mass start race and 28th place over 10 km classic. In February 2004 she clinched her third and last victory in the Continental Cup in Hommelvik classic over 5 km. She completed her 64th and last individual World Cup race in March 2004 in Lahti, which she finished in 30th place in the sprint. At Norwegian championships she was each together with Cecilie Risvoll Amundsen and Unni Ødegård with the relay of Molde og Omegn IF, in 2003 second and 2004 third.
Marit Roaldseth is married to the Norwegian cross-country skier Håvard Bjerkeli .