Huddersfield boosted their survival hopes by coming from behind to earn a 1-1 draw and deny Derby a sixth consecutive home win.
In a game low on quality and played in driving rain for long periods, Derby looked on course for another Pride Park victory when Tom Lawrence smashed in a spectacular strike.
Rain was falling heavily at kick-off with conditions set to get worse, and an early cross from Andre Wisdom almost caught Huddersfield out as it swerved in the wind.
Huddersfield had a chance four minutes later when Fraizer Campbell spun 12 yards out but his low shot was too close to Roos.
Lossl had to push away a Rooney free-kick as Derby continued to threaten, but Huddersfield had a great chance in the 39th minute when Junior Bacuna's corner found Campbell unmarked but he headed wide.
The rain eased by the start of the second and Huddersfield started strongly, with Campbell thumping a drive from the edge of the box against the inside of a post with Roos beaten.
But Huddersfield were trailing in the 61st minute when Rooney took a short corner, Shinnie rolled it across and Lawrence smashed it into the top corner from 20 yards.
Derby almost doubled their advantage eight minutes later when Wisdom whipped the ball across but Waghorn's diving header was straight at Lossl.
Lawrence sent a volley wide from another Rooney corner but Huddersfield levelled in the 81st minute.
Jayden Bogle's poor header was seized on by Toffolo, who ran into the box and squeezed the ball between Roos and his near post.
Huddersfield had a chance to go ahead three minutes later when Willock was put through but Roos got a hand to his low shot.