Kazim-Richards tapped home following a counter-attack 11 minutes into the second half as Rooney made it two wins from three games since being appointed as County's permanent boss.
The goal was part of an eventful afternoon for veteran striker Kazim-Richards, who missed an early sitter and after scoring was then fortunate not to concede a penalty for what seemed a clear handball.
He should have put Derby ahead in the first half but was guilty of an awful miss from in front of goal.
Nathan Byrne drifted away from Niko Hamalainen on the right and drew Rangers captain Geoff Cameron towards him before teeing up Kazim-Richards. The 34-year-old had only goalkeeper Seny Dieng to beat but inexplicably failed to make proper contact with the ball.
Rangers' two best chances of the first period both fell to Charlie Austin, making his first appearance at Loftus Road since returning for a second spell at the club.
After the Rams failed to clear Hamalainen's cross from the left, Kane pulled the ball back for Austin, whose shot was saved at point-blank range.
It proved to be a crucial save, with QPR failing to score when they were on top and then punished by a swift Derby break early in the second half.
QPR hoped signing Austin on loan from West Brom would end their tendency to drop points despite having plenty of possession.
He was a constant threat before being substituted late on, but it was a familiar story for the home side, who had won both of their previous two games following Austin's arrival, having failed to win in 10 before then.
They searched in vain for an equaliser and Lee Buchanan's clearing header prevented Hamalainen's cross reaching the waiting Austin.
The resulting corner by Ilias Chair struck the raised arm of Kazim-Richards and Rangers' players were incensed that a penalty was not awarded.
Roos then kept out Yoann Barbet's overhead kick to ensure Derby left west London with the points.