Forest Green goalkeeper Joe Wollacott was sent off in the first half as unbeaten Newport jumped to second in League Two after a 2-0 win.
Bristol City loanee Wollacott was handed a straight red card on 28 minutes for bringing down Tristan Abrahams after Ebou Adams' short back-pass put Rovers on the ropes.
Earlier, Wollacott's excursion outside the box gifted County the lead on three minutes. Abrahams pinched the ball off his foot for Padraig Amond to gleefully turn the ball into the inviting net.
After Wollacott's exit, Rovers rallied with Taylor Allen going close just before the break.
Rovers were a whisker away from parity on 75 minutes when Joseph Mills' arching free-kick clipped the crossbar after Carl Winchester was fouled by Abrahams.
Rovers were reduced to nine on 89 minutes after Matt Mills hobbled off as seven minutes of added time were played.
And to rub salt into the wounds, Newport wrapped it up when substitute keeper Lewis Thomas failed to keep out Ryan Haynes' 93rd-minute free-kick.