Roldan initially booked, then sent off, the wrong player in Sebastien Siani, before utilising the video assistant referee to determine that it was in fact Mabouka who required a red card.
Kerem Demirbay fired Germany in front three minutes into the second half with a powerful strike from the edge of the area.
Vincent Aboubakar pulled a goal back for the Lions to bring the score to 2-1.
The drama came on a landmark day for Joachim Low, who was able to celebrate his 100th win as Germany's head coach in his 150th game in charge.
Kerem Demirbay marked his full global debut with a brilliant goal and Timo Werner hit a brace as Germany booked their place in the Confederations Cup semi-finals with a 3-1 win against 10-man Cameroon on Sunday, but the game was marred by more Video Assistant Replay (VAR) confusion.
Roldan went on to produce a red card for Siani and he had to be persuaded by Cameroon players to look at the footage again, after which he dismissed Mabouka instead.
Cameroon's woes were compounded just two minutes later when Timo Werner's well-directed diving-header doubled Germany's lead.
Chile also progressed to the last four thanks to a 1-1 draw with Australia in the other Group B match to take place today.
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A fumble by Marc-Andre ter Stegen gave Cameroon a glimmer of hope on 78 minutes as Aboubakar's header flew through the German goalkeeper's fingers.
They dominated Australia for the first hour in Sochi, then weathered a Socceroos fight back, while in Kazan against Chile they showed guts in fighting back after conceding an early goal.
Veteran forward Tim Cahill collected his 100th global cap at Spartak Stadium, joining long-serving former goalkeeper Mark Schwarzer (109) as the only other Australia player to reach the landmark.
With the results, Germany finished top of the Group on seven points, followed by Chile, with five points.
Demirbay and Werner's goals were their first at worldwide level and Low added: "Players are always motivated and have developed a lot in recent years".
Alexis Sanchez then managed to get clear but the ball was taken off his foot by Ryan Milligan's last-ditch tackle.
Chile lost possession after Bravo had tried to play the ball out from defence and Robbie Kruse overcame a challenge from Gonzalo Jara to divert the ball into the path of Troisi to dink a cool finish over the keeper from six yards.
They could have grabbed a second right before half time when centre back Trent Sainsbury had golden opportunity, volleying over from 6 lawns when in acres of space after Chile protection quit, desiring offside that had not been there.
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