Both sides struggled for clear-cut opportunities in the first period but Ruben Rochina put the home side ahead in the 48th minute.
Rovers goalkeeper Jake Kean saved brilliantly from Billy Sharp to crucially preserve his side's advantage before Jordan Rhodes and Colin Kazim-Richards applied gloss to the scoreline.
Eric Black was in temporary charge following Steve Kean's departure the last time Rovers' took six points from six and current caretaker Gary Bowyer maintained his 100 per cent record following Saturday's 3-1 win at Barnsley in the wake of Henning Berg's sacking.
Alex McLeish was swiftly installed as Sean O'Driscoll's successor at Forest last week but has only managed one point from his first two games in charge.
The hosts started in lively fashion but required an excellent goal-saving tackle from Grant Hanley in the 10th minute with Forest striker Simon Cox poised to finish from close range.
Rovers sprung up the other end and Reds goalkeeper Lee Camp needed two attempts to grasp Rochina' shot following slick interplay from Martin Olsson and Josh King.
In the 17th minute, Henri Lansbury was inches away from giving Forest the lead as he crashed a 25-yard volley past the post.
Camp handed Blackburn a golden opportunity midway through the half, handling Danny Collins' backpass inside the area. From the resulting indirect free-kick Kazim-Richards drilled Danny Murphy's lay off into a well-stocked wall.
King had a speculative effort pushed around the post by Camp after the half-hour but, as half-time approached, an increasingly scrappy contest developed and it was a moment of fortune rather than quality that handed Rovers the lead three minutes into the second period.
Rochina took on the attack following an enterprising run by King and when the resulting shot was blocked by Daniel Ayala the ball rebounded back against his shin and flew past Camp.
Rhodes flashed a shot wide moments later before Camp's opposite number Kean produced a superb fingertip save to keep out Sharp's close-range header.
Morten Gamst Pedersen, on for Rochina, was found by Kazim-Richards on the overlap and played in Rhodes, who finished in composed fashion despite being driven away from goal.
A fine individual display from Kazim-Richards was capped in the 78th minute when he exchanged passes with full-back Adam Henley before lashing home emphatically.