Roldan scored the first of his two goals shortly after the match kicked off to set Seattle on their way, with Morris adding a second in the 38th minute before Roldan added the insurance just after the hour mark. Sebastian Lletget scored the Galaxy's only goal of the match in the 88th minute.
The Sounders struck for the opener just 12 minutes into the contest, when Morris got loose on the break down the left side and sent in a cross for a charging Roldan, who was there for the easy tap-in.
Morris then doubled the advantage in the 38th, helped by a pinpoint long ball assist from Nicolas Lodeiro that sent him down the left side again. The US international took the pass in stride and calmly slotted home the finish past Galaxy goalkeeper David Bingham.
Roldan rounded out the scoring for Seattle in the 61st minute, making a run behind the Galaxy back line to collect a pass from midfielder Joao Paulo before sending an audacious chipped finish over Bingham.
Lletget pulled one back for the hosts just before full time, scoring the game's final goal with a well-placed header off a cross from Rolf Feltscher that made it past Sounders goalkeeper Stefan Frei to spoil the clean sheet.
- 12' - SEA - Cristian Roldan | WATCH
- 38' - SEA - Jordan Morris | WATCH
- 61' - SEA - Cristian Roldan | WATCH
- 88' - LA - Sebastian Lletget | WATCH
MOMENT OF THE MATCH
: The pass from Nicolas Lodeiro to set up Morris's second goal was Seattle's Uruguayan maestro at his finest. When Lodeiro and Morris are connecting like this, the Sounders are tough to stop.
MAN OF THE MATCH
: Cristian Roldan deserves a mention for his two-goal effort from his right midfield spot, but it was Jordan Morris who was a terror down the left side all night. The 25-year-old is on fire at the moment, and continued what's shaping up to be his best season as a pro. He's now at seven goals and six assists in 13 games.