With 20 minutes remaining and Hammers still hopeful of salvaging at least a point, the Frenchman was shown the red card for apparently fighting with Johnson - who surprisingly escaped punishment for his part in the confrontation that was only brought to the attention of referee Dermot Gallagher by his assistant.
It just about summed up a hugely frustrating afternoon for Hammers, who will be rueing a missed chance to pick up three valuable points that were on offer against a seriously weakened Leeds side.
After selling off several of their most valuable assets during the January transfer window - including our very own Lee Bowyer who was given an expectedly rough reception on his return to Elland Road - and suffering a catalogue of injuries that forced Terry Venables to name midfielder Eirik Bakke as a makeshift striker, the Yorkshire outfit appeared to be there for the taking as Hammers fielded a virtually full-strength team.
Roeder had made four changes to the team that lost at home to Liverpool last weekend. Ian Pearce, recovered from flu, replaced Christian Dailly in the centre of defence, while Rufus Brevett came in for his full debut at left-back in place of the sidelined Nigel Winterburn.
Steve Lomas returned from suspension to take Trevor Sinclair's place in midfield, and Fredi Kanoute lined up for his first start since Boxing Day, lining up alongside Paolo Di Canio.
Roeder's men were given a scare after just 50 seconds, when Wilcox's dangerous free-kick from the right was left by Matteo at the near post and struck Lomas in front of goal, but the ball thankfully bounced wide for a corner.
Rather than let that damage their confidence, though, Hammers responded well and immediately pushed Leeds on to the back foot. Bowyer almost silenced the jeering home fans when he burst through the middle after four minutes, but Duberry got across to block his former team-mate.
Glen Johnson then surged into the area after dispossessing Bravo on the right and fed Bowyer, whose cross-shot was cleared, while Paolo Di Canio fired a free-kick straight at Paul Robinson.
The young Leeds keeper appears to be going head-to-head with David James for a starting place in England's friendly clash against Australia on Wednesday night, and the Hammers number one sent a clear message to Sven-Goran Eriksson in the 11th minute, when he pulled off a stunning save to keep the scores level.
A looped pass over the defence was misjudged by Repka, who stretched out a boot but only succeeded in diverting the ball over his keeper's head for what looked like a certain own goal. Amazingly, though, James scurried back and somehow managed to reach out and palm the ball wide. From the subsequent corner kick, he then did well to hold Bakke's point-blank header from eight yards out.
However, James won't have been happy with his reactions to
what proved to be Leeds' winner on 20 minutes. Seth Johnson
collected a return pass from Bakke some 25 yards out and, as the
defence backed off, curled a low shot that the Hammers keeper got a
hand to but couldn't prevent from nestling in the bottom corner
of the net.
The visitors did their best force a way back into the game before
half-time, with Cole producing a couple of moments of magic that
almost created clear openings, but too often the young midfielder
was isolated on the left, with Di Canio and Kanoute both struggling
to shake off the attention of Duberry and Matteo.
Hammers made a positive start to the second half, though, and once again it was Cole who provided the inspiration. Just two minutes after the restart, he picked the ball up just inside the Leeds half and surged forward before unleashing a fierce shot that cannoned off the post and back into play before being cleared.
Cole was denied again soon after, this time by Robinson. Bowyer broke free down the right and picked out Di Canio, who laid a first time pass square for Cole to fire in a rasping effort that the Leeds keeper blocked with his legs. To the delight of the home fans, Bowyer was then booked for contesting the goal-kick decision that followed after Cole and Mills challenged for the loose ball.
Tempers then began to fray all over the field, and the game exploded in controversial fashion in the 70th minute with the dismissal of Kanoute. With Dermot Gallagher seemingly oblivious to the fracas erupting between the Frenchman and Johnson, play was allowed to carry on for almost a minute before the flagging linesman finally caught the referee's attention.
After briefly consulting his assistant, the Banbury official brandished the red card - to the obvious fury of several of Kanoute's team-mates, who clearly felt that both parties should have been punished.
Roeder then brought on Defoe in place of Di Canio, and the young striker went close to snatching an equaliser with his first real involvement in the game. Collecting Cole's pass on the right with 11 minutes left, he cut inside Matteo, then switched on to his right foot again before firing in a shot that Robinson pushed round for a corner.
As Hammers became desperate in the closing minutes, Don Hutchison was thrown on to offer another attacking outlet and even James raced upfield to add his weight to a corner-kick, but the gamble was to no avail and the final whistle confirmed another miserable afternoon for Roeder and his men.
Hammers now face a two-week lay-off before travelling away again for a massive relegation battle against West Bromwich Albion, whose draw with Bolton Wanderers this afternoon at least kept both rivals within touching distance.