A lively encounter at the Rovers Academy ended with both sides reduced to 10 men, but more importantly, it was Rovers who earned all three points.
The home side raced into a three-goal lead at half time, thanks to goals from Brad Lyons, Joe Nuttall and Dan Butterworth.
Butterworth was shown a straight red late into the game, after George Byers was sent off for a challenge on Nuttall just a minute into the second half.
Despite the Swans scoring late on, Joe Lewis' strike proved to be only a consolation for the Welsh outfit, who returned home with nothing to show for their efforts.
Rovers started off the brighter and Brad Lyons gave the hosts the lead just 12 minutes into the contest when his low cross cannoned into the net off goalkeeper Steven Benda.
Swansea looked for a response, and Yan Dhanda dragged wide from the edge of the box after a ball from the left found him.
But a moment later and Rovers made it 2-0, with Nuttall scoring his fifth in two Development Squad games. Nice play from Lewis Travis and Stefan Mols saw the latter play the ball into Nuttall, who was left with an easy finish from close range.
The tails were up at this point and Butterworth marked his return from suspension with a third of the day; smashing home with his left foot after Benda failed to keep hold of the ball.
At the other end, a bouncing free kick from Byers forced Andy Fisher into a comfortable save, whilst Rovers had two further chances just before the break, with Hayden Carter and Nuttall both troubling Benda with headed attempts.
It was a clinical half for Rovers, who took their chances when they came and went in at the break with a big lead.
Rovers cause was helped just after the break when Byers was shown a straight red for a late challenge on Nuttall.
Rovers went for the throat and Butterworth twice went lose just before the hour, with Benda saving on both occasions after the forward got in behind the Swans backline.
Soon after and John Buckley saw Benda in his way from adding a fourth before Nuttall volleyed over Buckley's cross from the right.
At the other end, Jordan Garrick was denied by Fisher in a rare attack from the Welsh side.
The blot on Rovers' copybook came with 15 minutes remaining, when Butterworth saw red for an off-the-ball incident to level up the numbers.
In injury time, the visitors pulled a goal back through substitute Adam Lewis, who hammered home after a cross from the left reached him at the back post.
But Rovers had the game won in the first half, and the three points now sees Johnson's charges leapfrog their opponents, who now drop to the bottom of the division.
Rovers U23s: Fisher, Carter, Thompson, Travis, Magloire (c), Grayson, Buckley, Lyons (Paton, 80), Nuttall (Simmonds, 87), Mols (Vale, 87), Butterworth.
Unused substitutes: Winterbottom (GK), C. Doyle.
Goals: Lyons, 12, Nuttall, 20, Butterworth, 23.
Booked: Nuttall, 54
Sent off: Butterworth, 74
Swansea City U23s: Benda, A. Lewis, Govea (J. Lewis, 78), Maric, Harries (c), Cooper, Garrick, Byers, Biabi (Cullen, 66), Dhanda, Asoro (King, 46).
Unused substitutes: Paulet, Zabret.