After Harry Winter was sent off for a dangerous tackle on Chorley captain Andy Teague three minutes into the second half, Fylde still looked comfortable for a draw and had chances to win the game themselves.
But Roscoe popped up unmarked two minutes into injury-time to head home from six yards.
In a tight game, and Fylde’s first for three weeks, both sides failed to create any clear-cut chances in the first half hour.
Thenl Fylde’s James Dean and Paul Jarvis both had shots blocked from the edge of the area before Chorley’s Darren Stephenson sent a weak first-time volley inches wide. Dean then came close with a header which was deflected wide, and from the resulting corner on 36 minutes he tapped home a loose rebound from close-range only to be ruled offside.
The visitors had two chances within a minute to open the scoring four minutes before the break, as Jamie Vermiglio sent a vicious shot inches over the bar before Stephenson shot wide from the edge of the area.
A minute into the second half, Winter forced a save out of Jack Cudworth with a free-kick from the edge of the box but was then sent off for a two-footed challenge on Teague two minutes later – both players could have gone as Teague’s reaction was more suited to an icehockey rink than a football pitch.
The game petered out for a time before bursting into life again when new signing Ashley Dunn, making his first start for Fylde, was felled in the Chorley box racing on to a loose ball, but any thoughts of a penalty were waved away by the referee.
The best chances of the half for Fylde came on 66 minutes, when Cudworth pulled off two successive saves to deny first Dean and then Jack Dorney after he pounced on the rebound. And when Fylde won another free-kick 20 yards out, Paul Jarvis’ shot towards the top corner was tipped over the bar by Cudworth at full stretch.
Chorley began to make the extra man tell late in the game, and with two minutes remaining Vermiglio headed narrowly over after a well-worked move.
As the referee then indicated four minutes of injury time the visitors pushed forward again. and after they won a corner the ball found its way to Roscoe who guided his header home. Coasters Manager Dave Challinor was clearly disappointed and frustrated by some of his players.
Challinor said: “We speak an awful lot in the dressing room about the decisions that people make on and off the ball, and ultimately we’ve brought about our own downfall and we’ve decided the game, if you like.
“Harry’s decision to make that tackle resulted in a red card and he loses discipline, which we speak about all the time. Inevitably we’re going to lose an important player for at least four matches now.”
Of the overall performance, Challinor added: “We knew from our previous encounters with Chorley they were going to make it as bitty as possible and try and close us down. In the first half there wasn’t a lot in it but we were never in any danger, then the sending-off gives them impetus.
“But even with 10 men we’ve dominated and had some excellent chances. Their keeper has kept them in it. We ask people to do jobs but they score with a free header from a corner. “A draw may have been a fair result, but if we’d had all 11 men on the pitch I’ve no doubt we would have won.”
Fylde have half their league games still to play, but have slipped into the bottom half with this fourth defeat in seven Evo-Stik Northern Premier games and they now face a tall order to make their matches in hand count.
They return to league action at Bury against FC United on Saturday, before which they entertain Marine in a Lancashire FA Trophy quarter-final at Kellamergh Park tomorrow.
AFC Fylde: Hinchliffe, Haslam, Jarvis, Hughes, Taylor (C), Dunn, Dorney, Winter, Dean, M. Barnes (McCarthy 89), Booth (Farrell 82); Subs not used: Carden, Holland, Fleming.