In a game which saw the Pilgrims hardly threaten Rovers custodian Neil Sullivan's net, goals by John Spicer, James Hayter and Paul Heffernan were enough to give the visitors a vital three points and overcome any realistic fears of relegation.
Rovers took an early lead on the 15-minute mark courtesy of Spicer's rocket of a strike from 15 yards out.
Heffernan's sudden break down the left-wing began the play which was followed by the midfielder's subsequent cut back in to the path Spicer, who in turn struck past keeper Romain Larrieu to open up proceedings.
The Pilgrims' woes were doubled later in the half after Gareth Roberts managed to capitalise on a Larrieu goalkeeping error.
The defender, who had just completed a charging run down the left flank, was able to cross a pinpoint ball near the left-hand corner on to the head of substitute Hayter, who powered the ball over the exposed Frenchman to extend Rovers' lead.
Marcel Seip came closest in the first half to cutting the deficit for Argyle just after Hayter's' strike.
The towering Dutchman was the first to get a head to Paul Gallagher's free-kick from the right-flank, but his glancing touch went just wide of Sullivan's far post.
Jamie Mackie had earlier been ruled offside after his well-timed run beat marker James Chambers on the edge of the box.
Heffernan turned from provider to scorer near the end of the game to bag his first and Rovers' third with his close-range finish no match for Argyle's gloveman.
The deficit now leaves the home side teetering just above the relegation zone in 19th position with only two crucial fixtures remaining.