Rolland, who has yet to win a World Cup race after 15 top-10 finishes in downhill, earned her first medal at a major championship after charging down the 3.05-kilometre Streicher course in one minute 50.00 seconds.
Nadia Fanchini of Italy trailed Rolland by 0.16 in second. Maria Hoefl-Riesch of Germany, who won the super-combined title Friday, came 0.70 back in third.
"As a child I wanted to become a world champion one day," Rolland said. "Now it has become reality but it still feels like a dream."
Larisa Yurkiw, of Owen Sound, Ont., was 28th.
The 30-year-old Rolland was sidelined with injuries several times during her career, and saw the world title as a reward for fighting back.
"This is life, you have to believe to reach your goals one day," said Rolland, who fell four seconds into her run in the 2010 Vancouver Olympics downhill. "I wanted this medal today. I told myself before the start, 'Go fast, then you'll get it.'"
Going fast is exactly what Rolland did when she started as the final racer of the elite group. She beat then-leader Fanchini at every intermediate time.
In the finish area, French TV station TF2 showed Rolland her winning run. Commentator Carole Montillet, the 2002 Olympic downhill champion, shrieked when Rolland crossed the line, saying "it's not possible! It's unbelievable!"
Rolland was weeping as she talked about having "more difficult moments than nice ones" in her career. "It's mind boggling," she said. "I don't have the words. It's fantastic."
Rolland earned France's third medal of the worlds, after silver for Gauthier de Tessieres in the men's super-G and bronze for David Poisson in the downhill.
"I saw the men going really fast and I thought, I can go that fast as well," she said.
Rolland got her two career World Cup podiums on the same course during the World Cup finals in Schladming last year.
Fanchini, who won bronze in downhill at the 2009 worlds, was the second starter. She skied the turning middle part better than all the favourites, giving her more speed for the finish section. She led the race until Rolland wearing bib No. 22 came down.
Fanchini won bronze in downhill at the 2009 worlds in Val d'Isere, France, but then injured both her knees in a crash two weeks before the 2010 Vancouver Olympics. Then as she was still working her way back, she tore the ACL in her left knee again ahead of the World Cup race in Cortina d'Ampezzo in January 2011.
She only began training again after last season and at one point it seemed like she would be confined to giant slalom because her injuries wouldn't allow her to race the speed events.
"I can't believe it," Fanchini said. "I never gave up even when the challenge seemed almost too great. You've always got to believe in yourself. ... This medal is huge for me. Didier Cuche (the recently retired downhill standout) brought me luck when he signed my helmet. He wrote, 'Race for gold.'"
Nadia's older sister Elena Fanchini finished ninth.
Former overall champion Hoefl-Riesch, who won just one race on the World Cup circuit this season, has now made her second podium this week.
"It's fantastic to win a second medal," the German said. "I tried to risk everything. There were a lot of rolls and bumps. I am a bit lucky to come 0.04 in front of (fourth-placed Nadja Kamer). The course was OK, but visibility was changing a lot. You have to take how it comes. I am super happy."
After a cold night, the course was icier than during the training runs and the downhill portion of Friday's super-combined.
The frozen bumps caused many racers problems, leading to several crashes and delays.
Stefanie Moser, the third starter, flew into the safety netting while racing at 110 km/h. The Austrian's right ski came off after the binding broke on one of the icy bumps. She got up quickly and appeared unhurt.
Dominique Gisin of Switzerland also avoided injury after a nasty crash that also left her in the netting.
Defending champion Elisabeth Goergl of Austria came 1.48 back in tenth, and super-G champion Tina Maze missed out on a third medal after placing seventh, trailing Rolland by 1.21.
The Slovenian, who is likely to win the overall World Cup title this season, led Fanchini by 0.43 at one stage but was pushed wide in the middle section.
"I totally missed the race today," Maze said. "Until the middle part, I was attacking. I don't know what happened. I wasn't concentrated enough, I didn't have enough power. It was just tough to come down."
Lindsey Vonn left the championships Tuesday after an ugly crash in super-G that damaged her right knee and ended her season.
With five straight World Cup titles, the 2010 Olympic champion has dominated women's downhill racing. Vonn won gold at the 2009 worlds and silver in 2007 and 2011, and she also won three of five downhill events this season.
Teammates Julia Mancuso in fifth and Stacey Cook in sixth were the highest-ranked Americans.
"I had a solid run," said Mancuso, who also lost her lead in the middle section. "I got a little knocked by the terrain ... I got pushed wide, I saw Tina Maze got pushed wide. I didn't see Fanchini's run but Marion she just stayed on line the whole way and I think that was really important today."
Mancuso, who bronze in super-G, called champion Rolland "one of the fun girls. The French girls are always smiling. She's funny. They're relaxed — the classic French downhill attitude."
Cook led Fanchini by 0.92 at the second split and was the last racer in sixth to finish within a second of the winning time.
"I don't know where I lost it and I am a little frustrated," Cook said. "It's good to be fast in parts, I know I just need to put it all together."
The next race at the world championships is the men's super-combined on Monday.