After the embarrassment of a 5-0 loss against an ordinary Everton side at Goodison Park two weeks ago, the Hammers boss demanded a more disciplined and professional performance from his players, but instead saw his team capitulate completely with a display that was quite simply an insult to the Hammers fans that had made the long trip north up the M1 on Sunday morning.
And to compound Roeder's misery, Czech Republic defender Tomas Repka was sent off for a second bookable offence with 60 minutes gone - his second red card in just three games for the Hammers since arriving from Fiorentina last month.
By then, though, the Hammers were already 3-1 down after a totally inept first-half display in which Rovers hit the net three times in the space of 10 minutes after some simply dreadful defending.
With 18 minutes gone, Christian Dailly dithered with the ball on the edge of his area and was dispossessed by Flitcroft, who fed Grabbi before ghosting into the box to collect the return and head past Hislop.
Nine minutes later, England under-21 captain David Dunn curled a shot past a stranded Shaka Hislop from 25 yards out to make it 2-0 and 30 seconds later, it was three, as Tugay skipped down the right and sent in a cross that the unmarked Grabbi headed into the path of Johnson, who tapped in from two yards out.
With Rovers winning almost every challenge in midfield and enjoying almost unchallenged possession, it was clear that Hammers were in for another difficult afternoon, but a glimmer of hope arrived when Michael Carrick grabbed a goal back just five minutes before half-time, firing in a low shot from the edge of the area that beat Friedel on his left-hand side.
Boss Roeder acted quickly to improve matters further at half-time, replacing Christian Dailly and John Moncur with Hayden Foxe and young midfielder Grant McCann, and it appeared that the changes had provided a boost in confidence as the visitors started the second half in determined mood.
Just three minutes in came the moment that most will look back upon as the turning point in Hammers' fortunes. A Paolo Di Canio free-kick caused chaos in the Rovers defence and landed on the head of Trevor Sinclair just six yards out in front of goal. Somehow, though, Sinclair managed to divert his effort wide of the post.
11 minutes later came the hammer blow that killed all hope of a comeback. Tempers had threatened to boil over minutes earlier when Kanoute and Di Canio became involved in some petty pushing with Flitcroft, and referee Andy D'Urso was clearly out to prove his authority when he penalised Repka for what was nothing more than an innocuous trip on Repka before showing a second yellow to the Czech Republic defender.
Two minutes later, the capitulation began when McCann horribly sliced an attempted clearance into his own net and from then on the Hammers just caved in. Tugay added a fifth on 79 minutes and Jansen made it six two minutes later.
Substitute Craig Hignett completed the scoring in stoppage time and the final whistle became a relief from the pain for the handful of supporters who managed to stay in their seats for the entirety.
It is quite clear that Glenn Roeder has a massive task on his hands if West Ham are to avoid a season-long struggle against relegation this year and the Hammers boss certainly deserves more from the players who have shown a complete lack of commitment and courage to fight against adversity in the last three matches away from home.
Man of the match: Sebastien Schemmel - Along with Tomas Repka, the only Hammers player who could come out of the game with any credit. Schemmel didn't give up from the first minute to the last and displayed the kind of passion and determination to succeed that was clearly missing in all other areas of the team.
1 - After Moncur's foul on Johnson, the inswinging free-kick is headed over by Flitcroft.
9 - Dunn collects on the left after Sinclair loses possesion and runs at the Hammers defence before firing a shot over the bar.
10 - Carrick's dangerous cross from the right eludes both Kanoute and the Blackburn defence, while Di Canio's follow-up cross is cleared.
12 - Di Canio's fierce shot from 25 yards out flies just wide of the top left hand corner.
18 - GOAL. More defensive woes for the Hammers as Dailly fails to clear on the edge of the area and then loses the run of Flitcroft, who skips onto the cross of Grabbi and heads past Hislop. Blackburn 1 West Ham 0.
20 - Sinclair's deep corner from the right finds the unmarked Repka, whose firm header is cleared off the line.
26 - Johnson whips in a cross from the right that is superbly cleared by Repka.
27 - GOAL. Dunn collects possession in acres of space on the left, before advancing forward and curling a right-foot shot past the stranded Hislop from 25 yards out. Blackburn 2 West Ham 0.
28 - GOAL. Disaster for the shell-shocked Hammers as Tugay skips down the right and sends over a cross that the unmarked Grabbi heads back across goal for another unmarked team-mate, Johnson, to volley in a simple third. Blackburn 3 West Ham 0.
30 - Repka booked for foul on Grabbi.
35 - Tugay's corner is only cleared as far as Dunn, who volleys just over from 30 yards out.
37 - Di Canio wastes a glorious chance as he fails to make contact with an inch-perfect cross from Schemmel.
39 - GOAL! Hammers give themselves a fighting chance of staging a comeback as Carrick collects a return pass from Sinclair and curls in a low shot from the edge of the area. Blackburn 3 West Ham 1.
Added-time: 2 minutes.
Half-time: Blackburn 3 West Ham 1.
46 - Double substitution for West Ham, Foxe replaces Dailly and McCann replaces Moncur.
48 - After Hutchison is fouled on the right, Di Canio whips in a free-kick that drops on the head of Sinclair, six yards out, for what appears to be a certain goal. Somehow, though, the wantaway midfielder heads his effort wide of the post.
50 - Di Canio's quickly-taken corner is met by the head of Kanoute, but Friedel is equal to the effort.
54 - Kanoute booked for foul on Johansson.
54 - Di Canio booked for dissent.
57 - Grabbi booked for ungentlemanly conduct.
59 - Following an innocuous challenge on Grabbi, Repka is harshly sent off for a second bookable offence, making it two red cards in three appearances for the Hammers.
62 - GOAL. A simply embarrassing goal as Tugay's shot, heading wide of the target, is completely miskicked into his own net by McCann from just two yards out. Blackburn 4 West Ham 1.
69 - Hutchison's measured pass releases Kanoute, whose fierce shot from an acute angle is well-blocked by Friedel.
71 - Substitution for Blackburn, Short replaces Berg.
75 - Double substitution for Blackburn, Hughes replaces Grabbi and Hignett replaces Johnson.
79 - GOAL. The nightmare continues as Tugay fires a long-range effort over the despairing dive of Hislop to make it five. Blackburn 5 West Ham 1.
81 - GOAL. Just when we thought it couldn't get any worse....Dunn's fierce shot is only parried back out by Hislop and Jansen gratefully accepts the gift to make it six with nine minutes remaining. Blackburn 6 West Ham 1.
Added-time: 3 minutes.
90 - GOAL. Seventh-heaven for Blackburn but an absolute catastrophe for the Hammers as Hignett slides in to convert Jansen's cross. Blackburn 7 West Ham 1.
Full-time: Blackburn 7 West Ham 1.