The Timbers received goals from Eryk Williamson and Jeremy Ebobisse as they lost for the third time in five games since winning the MLS is Back Tournament last month near Orlando, Fla.
Williamson gave Portland a 1-0 lead in the 25th minute on his second goal of the season, using a feed from Felipe Mora to beat LAFC goalkeeper Pablo Sisniega.
Kaye tied the game 1-1 in the 37th minute, his second of the season. Wright-Phillips sent a ball through the penalty area with his head, and Kaye redirected the ball on goal with his right foot.
Rossi gave LAFC a 2-1 lead in the 41st minute with his 10th goal of the season, taking a pass from Brian Rodriguez in stride and scoring past Timbers goalkeeper Steve Clark.
LAFC increased its lead to 3-1 one minute into first-half stoppage time when Wright-Phillips took a pass from Francisco Ginella in front of the Timbers goal to score his fifth of the season and the 113th of his MLS career.
One minute later, and on the last touch of the first half, the Timbers got within 3-2 when Ebobisse scored his fourth of the season on a looping header off a long entry pass from Jorge Villafana.
LAFC’s Danny Musovski scored the lone second-half goal in the fifth minute of second half stoppage time, his second.