A first-half blitz from RSL saw the Utah-based club defeat DC United 3-0 as Rimando registered his 113th clean sheet, the most in MLS history.
Meanwhile in Columbus, a frantic finish saw the home-town Crew equalise with nine minutes remaining before Toronto FC triumphed 3-2 thanks to Luke Moore's 84th-minute header.
RSL (39 points) leapfrogged Seattle Sounders (38) into first position in the West's standings, while Dallas (36) claimed third ahead of Los Angeles Galaxy after their 3-1 home win against Colorado Rapids.
Jeffrey Cassar's RSL dominated from the first whistle of their clash with DC and deservedly opened the scoring in the 11th minute when Luke Mulholland picked out Joao Plata in the box and the pint-sized Ecuadorian nodded the ball home.
Just two minutes later and it was 2-0 with Christopher Schuler tapping in from Javier Morales' cut-back after DC had weathered an initial free-kick from their hosts.
The visitors from the capital were struggling and Schuler extended RSL's lead even further in the 24th minute with the central defender powerfully heading Morales' corner into the net.
While RSL were unable to add to their tally after half-time, another stellar performance from Rimando saw the home side maintain their advantage and claim three points.
The result made it eight games at Rio Tinto Stadium without a win for DC with the defeat following on from last week's 1-0 loss at Houston Dynamo.
Toronto notched their second consecutive victory in the United States' top tier of football but had to leave it late to secure the three points.
Gilberto struck for the second time in as many games to give Toronto the lead in the 43rd minute but Columbus were level at the break with Justin Morrow handballing in the box, allowing Crew midfielder Federico Higuain to convert the penalty.
The visitors moved ahead again in the 59th minute through Jonathan Osorio but Columbus thought they had snatched a draw when Justin Meram's ball into the box bounced past Toronto keeper Joseph Bendik and into the net.
But Ryan Nelsen's side took all three points back to Canada after Moore got his head to Collen Warner's corner with six minutes left.
The win saw Toronto rise to 32 points, five behind DC, with Nelsen's men sitting third in the Eastern Conference.
In other results, a Sebastien Le Toux brace saw Philadelphia Union prevail 2-1 against Montreal Impact and Diego Valeri's rocket from outside the box inspired Portland Timbers to a 2-0 win over Chivas USA.
