Donald dropped in a 20-foot birdie putt on the final hole to finalize a three-round score of 11-under 205 and put a little distance between him and Rose, who also carded a 69 for the round.
The 18th was one of four holes Donald birdied in the round. He slipped with a bogey on 15.
Should Donald hang on to win the tournament Sunday, he could move back into the world No. 1 ranking ahead of Rory McIlroy, who missed the cut on Friday.
Ernie Els, who redesigned the Wentworth course where the tournament is being played, shot a 70 and had some sharp words about the dry condition of the greens. "It's such a pity. You put so much work and effort into it," Els said. "Why are the greens getting out of control?"
James Morrison was another player who wasn't happy with Saturday's round. The second-round leader fell apart in the third round, finishing with a nine-over 81 and relegation to 11th place.