Goalkeeper Stefan Frei was credited with two saves as the Sounders (14-5-6, 48 points) moved two points ahead of Sporting KC (13-6-7, 46 points). Seattle, which has a game in hand, snapped a six-game winless drought in Kansas City (0-4-2) that dated to 2013.
Johnny Russell scored for Kansas City, pulling the hosts within 2-1 in the 60th minute.
Though Sporting KC dominated possession in the final half-hour, it was unable to come up with the equalizer.
Roldan scored in the 31st minute to give the Sounders, who were coming off a 3-2 loss to Club Leon in the Leagues Cup final on Wednesday, a 1-0 half-time lead.
Brad Smith's cross from the left wing found Roldan, the trailer, unmarked in the center of the penalty area and his powerful one-timer from 15 yards out went off goalkeeper Tim Melia's left hand before trickling into the bottom right corner of the net.
Bruin made it 2-0 in the 55th minute after a Kansas City turnover deep in its own end of the field. Raul Ruidiaz intercepted Graham Zusi's pass at the top of the 18-yard box and dribbled his way between three defenders before trying to lob the ball over Melia. Instead, the ball deflected high into the air and toward Bruin, who put a header from 10 yards into the side netting, just inside the right post.
Sporting KC finally got on the board three minutes later, as a free kick from about 30 yards out was headed away from the center of the penalty area by Sounders defender Nouhou Tolo but fell directly to Russell at the top right of the 6-yard box. His shot snuck between Frei and the near post.