Mark-Anthony Kaye opened the scoring for LAFC in the first half and Adama Diomande doubled the lead in the 88th minute before Vela capped the scoring with another of his trademark curling left-footed strikes.
The Mexico international picked up the ball near midfield and split two Crew defenders before cutting in on his left foot and bending home a shot from outside the box.
"I think we are having a great season, but we want more," Vela said after the match.
In the club's second season in the league LAFC has the look of a strong contender. The club sits atop the Western Conference standings on 27 points through 12 matches.
One of the teams looking to beat LAFC to the top spot in the West is the Sounders, who got a stunning winner from Roldan against the Houston Dynamo just a week after his blast earned the club a 1-1 draw with Minnesota United.
A clearing header from the Dynamo fell to Roldan 25 yards from goal and the midfielder lashed home with his second touch to secure a 1-0 win for Seattle.
The Sounders, who brought in a new designated player this week in the form of Xavier Arreaga while also managing to sign former fullback Joevin Jones, currently sit third in the West, five points back of LAFC with a game in hand.
Seattle is level on points with the second-placed LA Galaxy, who fell 2-0 to New York City FC on Saturday night.
Both Roldan and Vela could play key roles for their respective national teams in this summer's Gold Cup, though the LAFC star's position with the Mexican national team under manager Gerardo "Tata" Martino remains in question.