And that fine comeback by Daniel Farke's side on Tuesday night saw them go above Tottenham Hotspur in the table and up to 15th.
They remain six points clear of the relegation zone, after struggling West Ham conceded a last-gasp equaliser against Manchester United.
Until midway through the second half this had looked like being another step forward for Chelsea, who had been steadily growing into an exciting, watchable outfit under their new head coach.
Joao Pedro got the opener with a lovely finish before Cole Palmer's penalty made it two to have the hosts seemingly coasting to victory against a Leeds side who had offered next to nothing.
Chelsea have looked newly confident in possession since Rosenior's appointment but the manner in which they threw away two points was alarming.
Lukas Nmecha's penalty after Jayden Bogle had been fouled made it 2-1.
Jayden Bogle (left) won the penalty that kickstarted Leeds' excellent comeback at Chelsea. (Image: Nick Potts/PA Wire)
Then, a moment of unbelievably casual defending allowed Bogle to create chaos from which Noah Okafor pounced to level, as old habits reared their head for the home side.
Chelsea went ahead after 24 minutes. Enzo Fernandez knocked it short for Palmer who turned and found the forward run of Pedro with a perfectly weighted through ball.
The striker measured his run to keep onside before clipping a fine finish over the advancing Karl Darlow for his 10th league goal of the season.
Much frustration has been spent by home fans in west London this season over the slow, ponderous speed of their team's passing.
Under Rosenior there have been encouraging signals of a more dynamic approach to possession and here again the ball moved with urgency, particularly through midfield where Chelsea constantly seemed to outnumber Leeds.
The hosts had dominated creatively without much input form Estevao, so often their saviour in moments of inertia during Palmer's recent fallow spell.
Finally the teenager burst to life at the start of the season half, dancing his way through the defence before firing a low effort wide.
Leeds gifted Chelsea their second. Robert Sanchez, a virtual spectator in goal, found a way to make himself involved with a terrific long pass to release Pedro.
In an uncanny mirroring of the penalty he won against Wolves on Saturday, Jaka Bijol needlessly shoved the striker the to ground, with Palmer gratefully making it 2-0 from the spot.
Leeds looked well beaten but they were soon handed a lifeline when Moises Caicedo tripped Bogle as he burst into the box down the right.
Nmecha sent Sanchez the wrong way with an emphatic penalty to restore jeopardy to the contest.
It breathed life into Leeds and at the same moment drained Chelsea of their composure.
Bogle sparked panic as the defence allowed a bouncing ball to go unchallenged for, somehow holding off three players in blue before Josh Acheampong inexplicably presented it to Okafor who tapped into the empty net.
That left Chelsea to begin again from scratch.
Pedro Neto bent a cross-shot inches wide as they looked to steal it, then Pedro nodded a free header against the bar.
But Chelsea saved the worst for last, as Palmer produced an unbelievable miss from virtually on the goal line, as the points slipped away.