Major League Soccer-leading Seattle will face the Philadelphia Union on Sept. 16 in the final in Chester, Pennsylvania. Philadelphia advanced on the road Tuesday night, beating FC Dallas on penalty kicks.
Seattle reached the final for the fifth time since joining MLS in 2009. The Sounders won three straight Open Cups from 2009-11, and lost at Kansas City on penalty kicks in 2012.
Chad Barrett opened the scoring in the sixth minute, and Rose made it 2-0 in the 33rd when he headed Marco Pappa's corner kick high into the upper left corner past goalkeeper Sean Johnson. Near the end of the 58th minute, Rose made it 3-0 when he headed in a target ball from Pappa.
The Sounders added three goals in a 4 1/2-minute span, with Obafemi Martins connecting in the 79th, and Cooper in the 82nd and 84th.