Darren Ferguson was delighted with a third straight win since returning as Peterborough boss.
A 72nd-minute Jonson Clarke-Harris penalty gave Posh the lead and midfielder Hector Kyprianou sealed the win with his second goal of the campaign deep into stoppage time.
The midfielder drifted in unchallenged from the left corner flag before firing high into the top corner from a tight angle to spoil the party in Forest Green manager Duncan Ferguson’s first home game in charge
Peterborough manager Darren Ferguson said: “It was a magnificent goal, a really good result and professional performance.
“At the moment we’re finding ways of winning games.
“We knew it would be difficult as I knew the players would work hard for Duncan.
“It was one of those games when you just have to find a way of winning. We needed patience and we needed discipline and we got them.
“It was a really good result and a professional performance. I thought we were really disciplined.”
Clarke-Harris opened the scoring from the spot after winger Jordon Garrick bundled over opposite number Kwame Poku in the box.
Rovers improved after Clarke-Harris’ 18th goal of the season.
Posh goalkeeper Will Norris did well to turn a shot from striker Amadou Bakayoko over the crossbar one minute later and defender Brandon Cooper was left holding his head in his hands after nodding over from eight yards.
But the defeat left Rovers four points adrift at the foot of the League One table.
A disappointed Forest Green boss Duncan Ferguson said: “It’s not as if Peterborough were cutting us open. They didn’t have too many chances and they’re pushing for promotion.
“It wasn’t a 2-0 game. It was tight and we had a good shape about us. I thought we played well and you could see the organisation.
“It’s disappointing, but it’s encouraging as well with the work the lads put in. The penalty put us on the back foot, but it was a penalty.
“We don’t seem to be getting the breaks.
“We’ve got to pick ourselves up, make these players better and make them believe. I’m giving everybody a chance and I’m giving everybody a go.”
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