Match report: Plymouth Argyle 2 Doncaster Rovers 0
Coppinger saw red after grabbing at Argyle keeper Luke McCormick, who gloated in the face of Liam Mandeville following a late penalty miss.
It only heaped frustration on Rovers who struggled to find their rhythm in the top of the table clash.
By the time Mandeville struck the outside of the post from the spot, Rovers found themselves two goals down.
A mistake from Andy Butler allowed Graham Carey in for a sublime finish before Jake Jervis gave the hosts a cushion from the penalty spot, giving Plymouth a first win in four attempts in the league.
Rovers failed to build on a strong start in a game where clear cut opportunities for either side proved hard to come by.
And they failed to score in a league game for the first time this season.
Darren Ferguson kept faith with the side that started in the 4-3 win over Stevenage a week earlier.
Rovers made an excellent start, forcing the hosts back with strong pressing and probing passing.
They were close to going ahead inside the first two minutes. Niall Mason charged forward and pulled a ball back to Tommy Rowe who shot first time but straight at McCormick.
Plymouth delivered a warning on seven minutes when the unmarked Carey flicked a header over the bar from close range.
But Rovers continued to be the stronger, building attacks well, particularly down the flanks.
Plymouth enjoyed their own success in wide areas and Jordan Slew arguably should have done better when he met Connor Smith's cross only to scuff it at Marosi.
Coppinger was a lively presence for Rovers, often creating opportunities from nothing.
One superb cross caused havoc in the Plymouth back line with Yann Songo'o wildly sliced just wide and out for a corner.
It took a brilliant hooked clearance from Mathieu Baudry, heading back towards his own goal, to prevent Ryan Donaldson's cross from reaching danger.
In such an even contest, it was always seemed likely that it would take a mistake to break the deadlock and it proved to be just that which led to Plymouth taking the lead on 33 minutes.
Andy Butler looked to play a short pass out to Rowe, who was rapidly closed down by Carey. The wide man galloped forward into space and curled a stunning shot past Marosi from the edge of the area.
Rovers twice went close to equalising in the following minutes.
Coppinger's free kick was headed back by John Marquis and Craig Alcock slammed a shot which McCormick did well to parry.
And moments later the Plymouth keeper palmed away a close range header from Butler.
The hosts were growing in confidence and began to take command of the ball, with the half petering out somewhat for Rovers.
More to follow.