The 35-year-old kept out David Unsworth and then foiled Rob Hulse in the 87th minute after United keeper Paddy Kenny had saved Lucas Neill's spot-kick.
Rovers, propping up the league, had been handed a half chance seconds into the game after David Bentley steamed on to a poor Kenny clearance.
With the United keeper scampering back, the Rovers midfielder picked out Francis Jeffers who powered his header over the top from eight yards.
The former Charlton Athletic striker was handed a similar chances minutes later when Brett Emerton was given time and space to cross from the right flank but this time he failed to connect with only Kenny to beat.
Rovers were carved open in the 13th minute when Unsworth's long ball down field fell nicely for Rob Hulse who took the ball in his stride as he raced into the area but blasted his right-foot shot high over the bar.
United had to adjust on 17 minutes with striker Danny Webber limping off to be replaced by France under-21 international Christian Nade.
Midfielder Michael Tonge almost found a way through with a free-kick hit low and hard but the ball was scooped up at the near post by keeper Friedel before being hammered clear.
United escaped minutes later with Robbie Savage's precise cross falling at the feet of Benni McCarthy but, before the little striker could react, David Sommeil was quickly in to hack the ball away.
Rovers skipper Neill tried his luck six minutes before the interval with a right-foot strike from the edge of the box but the ball curled inches wide of the mark with Kenny scrambling across his line.
Tonge squandered a chance heading a Chris Armstong cross wide from close range before Rovers were awarded a penalty in the 70th minute after Unsworth nudged Benni McCarthy in the back as he jumped to meet a Morten Gamst Pedersen cross.
Kenny produced a stunning save diving to his left to stop Neill's spot-kick.
Mikele Leigertwood saw his 20-yard strike pushed away by Friedel before United were handed a penalty in the 79th minute after Zurab Khizanishvilli was punished for pulling back Hulse.
Unsworth powered his spot-kick to Friedel's right but the keeper was quickly down to push the ball away.
United should have wrapped up the game three minutes from time after Neill handled in the area but Friedel dived to his left to block the ex-Leeds striker's penalty.
Friedel kept out Hulse deep in injury time saving with his legs after the striker turned quickly in the area.