The 23-year-old emerged from a seven-way tie to snatch the lead in California.
The American carded five birdies and two bogeys en route to a final-round 67.
The top 17 names on the leaderboard are separated by just four shots in California.
Paul Casey cut a calm and relaxed figure after keeping himself in the hunt at the PGA Championship on Saturday.
How does Brooks Koepka feel ahead of the final round of the PGA Championship? Confident.
Round of 72 does little to enhance his chances of a 16th major.
China’s Li Haotong holds the halfway lead at Harding Park.
Tommy Fleetwood weighs in on the state of his game after playing himself into contention at the PGA Championship.
Fleetwood, Rose and Casey are hoping to break the 101-year drought.