Rocque and her Edmonton rink stole two points in the eighth end and hit out for the win after South Korea scored a single in the ninth.
"Honestly, this is unexplainable," Rocque said. "We came into this tournament really wanting it, and it's awesome to see all our hard work pay off."
In men's play, Canada's Braden Calvert settled for a fourth-place finish after dropping a 7-5 decision to Norway's Eirik Mjoeen in the bronze-medal game.
Rocque and third Keely Brown, second Taylor McDonald, lead Claire Tully and alternate Alison Kotylak are the first Canadian team to win the world junior women's title since Saskatchewan's Marliese Miller (now Kasner) won the championship in 2003.
"It's almost less pressure knowing Canada hasn't won the gold (in 11 years)," Rocque said. "It's awesome to get it again."
The Canadian rink had won six games in a row entering the final. Rocque had last-rock advantage because of her win over Kim in the Page 1-2 playoff game.
Kim led 3-2 after six ends but Canada regained the lead with a double in the seventh. Rocque added another deuce in the eighth end when Kim's takeout attempt rolled too far.
"They are a very strong team," Rocque said of the silver medallists, the first South Korean team to qualify for this event. "She made a clutch shot in the ninth end and we knew it would be right down to the bitter end with them. It was a well-played game."
"I'm so proud of the girls, they just played great all week and we just had an awesome week," she added. "I couldn't ask for anything more."
Russia's Alina Kovaleva defeated Sweden's Isabella Wranaa 11-4 to claim the bronze medal.
Switzerland's Yannick Schwaller won the men's gold with a 6-5 victory over 2013 champion Kyle Smith of Scotland.
In the bronze-medal game, Calvert stole two in the ninth to pull even heading into the 10th end. Norway had the hammer and scored two when Calvert came up short on his final freeze attempt.
"We're disappointed with our play today and know we can play better," said Calvert. "We're hungry for more. We just got out of the starting gate a little slow today and picked it up late, but not soon enough."
His Winnipeg team included Kyle Kurz, Lucas Van Den Bosch, Brendan Wilson and alternate Matt Dunstone.