The Polish international condemned Alan Pardew's side to a third successive Championship defeat.
Following their defeats last Saturday, both West Ham and Derby had needed more than a draw to get their play-off ambitions back on track and, in the end, it was the victorious visitors who claimed maximum points.
Certainly, the Hammers could not have got off to a worst start as Gavin Williams was crocked by a crunching fifth-minute tackle that saw him replaced by Mark Noble.
And the teenage substitute had barely got into the game before the towering Raziak arrived in the six-yard box to head the overlapping Richard Jackson's inch-perfect, left-wing centre past the exposed James Walker with just ten minutes on the clock.
Noble, however, went close with a dipping 25-yarder that just flew past Lee Camp's right-hand angle and then Sergei Rebrov nodded over a pinpoint cross from former Ram, Chris Powell.
West Ham were certainly looking more convincing going forward than they were in defence, and after Carl Fletcher was booked for a lunge on Ian Taylor, his aggression in the Derby area was also responsible for the equaliser on 26 minutes.
Marlon Harewood nodded down Rebrov's cross and the four-times capped Welsh international battled and baulked every inch of the way to wrestle possession from Inigo Idiakez and drill a low 15-yarder into the bottom left-hand corner.
Four minutes before the break the home side looked all set to take the lead when Noble's threaded pass sent Harewood bursting clear.
But as the striker rounded Lee Camp on the edge of the box, the County keeper cynically bundled him over. A mandatory red card looked a mere formality, but referee Mason controversially only produced yellow and the disgusted Hammers saw the resulting free-kick come to nothing.
The pardoned Camp then foiled Nigel Reo-Coker on the stroke of half-time.
Just after the restart Fletcher saw Jeff Kenna nod his powerful header off the line and then Harewood skied over with the goal at his mercy.
At the other end, Morten Bisgaard intercepted from Noble and curled his 18-yarder inches wide in what was to prove a timely warning for West Ham.
For, on 63 minutes, the unmarked Rasiak hooked home his 11th goal of the season when Tom Huddlestone nodded on Idiakez's inswinging corner to the undisguised delight of Derby's travelling fans.
To chants of 'You don't know what you're doing' the under-pressure Pardew withdrew Rebrov in the hope that Teddy Sheringham could yet again save the Hammers.
It was an big ask of the 38-year-old striker and Camp added a final insult to injury when he acrobatically clawed away Luke Chadwick's goalbound curler to confirm Derby's victory.