Allardyce was relieved of his duties at St James' Park in January 2008 after just eight months in charge, but marked his first trip back to Tyneside with a win as the Magpies failed to record a fourth successive Premier League success.
On a night when Andy Carroll did his England chances little harm with a fine goal and Joey Barton once again courted controversy in a clash with Rovers' Morten Gamst Pedersen, it was the visitors who come out on top after nullifying the threat posed by Carroll and his team-mates for long periods.
Instead, it was substitute Jason Roberts who earned his manager's plaudits with an 82nd-minute winner.
Allardyce said: "Our match-winner at the moment is Jason Roberts.
"He was nearly our match-winner against Chelsea, he was our match-winner against Wigan and he made the goal for himself again, and he won us the game.
"It was a fantastic victory for us, a really pleasing one for us all and one I think in the end, we deserved.
"We changed the system to cope with the attack of Newcastle United.
"The very potent front two and the delivery from the wide men has been an outstanding force for them in the last three games, and we felt we had to stop that."
Hopes were high for the home side as they went into the game on the back of a run which included wins over arch-rivals Sunderland and Arsenal.
However, they were undone as much by their own mistakes as by Blackburn's pugnacious approach.
Cheik Tiote's uncharacteristic early slip presented Pedersen with the perfect opportunity to open the scoring with just three minutes gone, and the Norwegian needed no second invitation.
The Magpies were laboured in their efforts to force their way back into the game, but the scene was set for a second-half onslaught when Carroll powered home Barton's 47th-minute free-kick.
But with Newcastle pushing for a winner, they contributed to their own downfall once again two minutes from time when Mike Williamson was muscled off Paul Robinson's clearance by Roberts, who then reacted first to slide a shot past keeper Tim Krul.
Newcastle boss Chris Hughton said: "Frustrated is probably the word that comes to mind because overall, was it a game we deserved to lose? I would say categorically no, it wasn't.
"Sam came with a side that played five at the back, four in midfield and one up front to make life difficult for us.
"That being the case, you have got to be a good enough side in possession and you have got to create enough chances.
"The game hinged on not the opportunities that they created, it was more our own downfall, two errors that we made which they capitalised on."
However, much of the debate after the final whistle surrounded the 50th-minute incident in which Barton appeared to catch Pedersen in the ribs as he ran past him, a coming together which was not spotted by referee Mike Jones.
Hughton admitted he had not seen the clash, unlike Allardyce, who nevertheless kept his own counsel on it.
He said: "I'm not really going to talk about that because I don't want to detract from our victory.
"Whoever will see it will see it and do whatever needs to be done."