Gordon Moffat’s side remain two points clear of Benburb ahead of the sides’ crunch clash at New Huntershill this weekend.
A double from Gary Giffin and goals from Jamie Hunter and Greg Fernie (pictured right)put Rossvale in control.
And although second-bottom Lesmahagow rallied to pull two goals back, the home side held on to claim three more points.
Rossvale totally dominated the first half and almost went ahead in the 10th minute when Lesmahagow keeper Daniel Tobin was lucky not to be sent off for handling the ball outside his box when he came sliding out to stop a ‘Vale attack.
From the resulting free-kick Kirk Forbes curled the ball into the box only to see it bounce off the upright.
Greg Fernie was unlucky five minutes later when he was one on one with the keeper but Tobin managed to put it out for a corner.
Within minutes he had another chance but keeper managed to clear his lines and get the ball upfield to his relief.
However Rossvale broke the deadlock when skipper Jamie Hunter, and great interplay between Fernie and Liam McGonigle, was sent through on Tobin and curled the ball past the keeper.
Rossvale were totally dominant and another fine move came on the half-hour mark saw McGonigle sent Gary Giffin through on Tobin to put ‘Vale further ahead.
But the best was still to come and 10 minutes later a great move which started deep in the Rossvale half finished up with McGonigle finding Hunter who then played through to Fernie and he picked out Giffin to score his second and the ‘Vale’s third.
Lesmahagow had no answers to the football that Rossvale were playing at this stage and it was a case of how many Vale would score as each attack was just ripping the ‘Gow defence apart.
Rossvale went further ahead ten minutes into the second half when McGonigle’s cross found Fernie at the back post to score with a fine header
Fernie then nearly got another moments later when he hit the post and then had a penalty claim turned down .
On the hour mark Lesmahagow had their first main shot on goal and a couple of minutes later their new signing ex-Motherwell player Mark Fitzpatrick headed in from a corner and the challenge was on.
Whilst Rossvale took their minds of the game, ‘Gow came right back into the game with a confidence they didn’t have in the first half where they couldn’t break down the ‘Vale defence.
But they were now getting through and with six minutes to go Chick McCole hit a strike from 20 yards which flew in at the back post and ‘Gow were back in the game.
Rossvale sub Steven Seaton was unlucky not to score soon after coming on but could only find the side netting.
Lesmahagow finished the stronger side but it was the work that Rossvale put in in the first half that saw them come out winners in the end.