An eventful match saw the Owls give away a spot kick and Glenn Loovens was subsequently sent off as he brought down Matej Vydra in the box after just four minutes.
Vydra scored from the spot but it would take until late in the game for Derby to break down battling Wednesday again, with substitute Bradley Johnson scoring the second.
In a game of many talking points, Rowett felt that Keiren Westwood could have been fortunate to escape a red card as he came rushing out of goal to block, with the ball hitting somewhere on his upper body.
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And like last week, when Kieran Lee was denied a penalty against Bolton, there was another dismal decision from an Owls point of view as Steven Fletcher was brought down by Richard Keogh yet the referee played on.
“You could argue that the (Derby) penalty was enough punishment but I’m sorry to say I was pleased with the red card,” said Rowett of Loovens’ sending off.
“I felt we then should have scored again, disappointed we didn’t make more of that.
“I then felt that Westwood used his hand (outside the box) whether it was intentional or not, but I felt that could have been another red.
“I also felt that there could have had a penalty at the other end. I’m not sure why Fletcher would go down, it look an obvious penalty.”