A goal in added time from Nottingham Forest striker Darius Henderson saw Rovers lose their first Ewood encounter of the 2013-24 season.
The game seemed to heading towards a goalless draw as the match went into injury-time but when goalkeeper Jake Kean failed to claim a high ball in a challenge with Jamie Mackie it bounced loose to Henderson and he fired into the empty net.
It was harsh on Rovers as they had worked hard in a tight and tense match in which chances were at a premium.
A point would have been fair in a competitive game between two closely matched teams, but it wasn't to be.
Gary Bowyer made two changes from the side that drew with Derby County on the opening weekend of the season.
Following his goalscoring heroics at Pride Park, Leon Best was given his first start, replacing the injured Ruben Rochina.
The other change saw Chris Taylor get the nod ahead of Josh King who dropped to the bench.
The first half was a niggly affair, the referee's whistle often heard as the game struggled to gain any momentum.
Both sides had chances, Jamie Paterson saw a shot beaten away by Jake Kean, whilst Scott Dann and Jordan Rhodes both missed with headers in the six yard box.
The last action of the half saw Ewood debutant Tommy Spurr head off the line to deny Radoslaw Majewski.
The second half was slow to get going, Rovers' best opportunities coming from Alan Judge deliveries into the area.
At the other end, aside from an Andy Reid free-kick that curled just beyond the post, and a shot from substitute Matt Derbyshire that was well blocked by Scott Dann, chances were at a premium.
Rovers had the majority of play in the second half, but like the visitors they couldn't carve out any clearcut chances.
Just when it looked like the game would end with a hard fought point for both sides it was the visitors who grabbed an unlikely winner.
A high ball into the box saw Rovers 'keeper Jake Kean race to the corner of his area to claim the ball under pressure from Jamie Mackie, but Kean couldn't hold and that allowed striker Darius Henderson the simple task of stroking the ball into the empty net from 12 yards.
It was a cruel way to end the game Rovers had done well against a highly-fancied Forest side, both sides defended well throughout and restricted chances until that lapse at the death.
ROVERS: Kean, Kane, Dann (c), Hanley, Spurr, Taylor (sub King 68 mins), Marrow, Lowe, Judge, Best, Rhodes.
Subs not used: Eastwood (GK), Dunn, Olsson, Songo'o, Morris, Evans.
FOREST: Darlow, Lichaj, Guedioura, Cohen, Henderson, Lansbury, Reid (sub Halford 82 mins), Paterson (sub Mackie 60 mins), Wilson, Hobbs, Majewski (sub Derbyshire 64 mins).
Subs not used: De Vries, Harding, Collins, Miller.
Goals: Henderson 90+1.
Booked: Lichaj, Lansbury, Henderson