Darren Bent renewed hopes of a revival with his 15th goal of the campaign in front of the Addicks' biggest ever away following in the Premier League, but a Hermann Hreidarsson own goal, Roberts' second of the game and substitute Matt Derbyshire's late strike made the points safe for Mark Hughes' men.
Both sides arrived in Blackburn on the back of 1-1 draws, but while Hughes named an unchanged side for the fourth game running, Alan Pardew welcomed back Hreidarsson, Matt Holland and Marcus Bent into the starting line-up.
Despite the vociferous support from the 6,000 travelling Charlton fans, who embarked on Operation Ewood in over 70 free coaches and three subsidised planes, it was the home side who made the better start.
Roberts showed what he was all about on 25 minutes, when he used his power to hold off Talal El Karkouri, before unleashing a long-range strike, which drew Scott Carson into a fine diving save.
On 38 minutes, Benni McCarthy fired narrowly wide with an acrobatic overhead kick and straight from Scott Carson's goal-kick, Marcus Bent flicked the ball on to his namesake Darren, but after lobbing Brad Friedel, the England striker was denied the opener by the linesman's offside flag.
The visitors threatened again early in the second half, when Marcus Bent again supplied a clever through ball, but with a clear sight of goal, Holland could only pick out the side of the net.
On 54 minutes, Morten Gamst Pedersen sliced a volley wide, before almost providing the perfect curling cross for Roberts, but the former Wigan frontman's faint touch wasn't good enough to beat Carson.
But with an hour of the game played, Roberts did get his goal. After receiving the ball at his feet, the Grenada international held off Hreidarsson, turned and drove into the box, before seeing a powerful drive fumbled into his own net by the Charlton keeper.
Thatcher was then sent for an early bath just three minutes later, following his second bad foul on David Bentley of the afternoon, before Charlton's depleted numbers got themselves back into the game.
On 71 minutes, a long free-kick into the area was flicked on by Marcus Bent, Stephen Warnock looked to head the ball back to his keeper, but when the over-hit pass came back off the underside of the bar, Darren Bent was first to react and the England striker powered a diving header into the roof of the net.
But the sides were level for just six minutes. After Brett Emerton's barnstorming run across field, Pedersen's cross from the left deflected off Hreidarsson and rolled past a wrong-footed Carson and inside the near post.
Rovers' third and best goal of the game arrived on 80 minutes, after some fancy footwork between McCarthy and Pedersen down the left. The South African's stylish back-flick fed Pedersen on the by-line and the Norwegian winger cut the ball back for Roberts to fire home.
McCarthy was soon substituted for Derbyshire and the England Under-21 star smashed home Rovers' fourth with virtually his first touch, after latching on to Aaron Mokoena's header down the right flank.
Substitutes Tugay and Shabani Nonda both blazed over the bar, before Darren Bent was denied his second of the game by the bar in time added on.