Rimando stopped a penalty kick by Robbie Keane in stoppage time to preserve RSL's season-opening 1-0 victory over the L.A. Galaxy.
Joao Plata scored the only goal of the night in the 80th minute off a feed from Kyle Beckerman. Plata slipped past Omar Gonzalez outside LA's box, and he finished easily against Jaime Penedo to give RSL their fifth straight opening-day victory.
The win made new head coach Jeff Cassar a winner in his debut.
Plata scored just four minutes after Luke Mulholland found the back of the net, only to have the goal waved off by a questionable offside flag.
Rimando, who had several spectacular stops among his nine saves, dived to deny Robbie Keane from the penalty spot in the 93rd minute after Tony Beltran undercut Rob Friend as he leapt for a ball into the box from Omar Gonzalez.
Rimando posted his 109th career shutout, just three off Kevin Hartman's league record.
RSL next heads to San Jose on March 15 in a game that will be televised at 8:30 on ABC 4.