Rovers felt aggrieved when the original fixture was abandoned in August, with them leading 3-1, due to a torrential downpour.
And they were left feeling distinctly under the weather again after goals from Dale Stephens and Simon Church consigned them to defeat in the rematch.
Addicks boss Powell said: "It was a deserved win, a brave, committed performance under some pressure.
"We knew it was our game in hand and we all knew what happened in abandoned game - so we needed to make most of it.
"We didn't perform in the abandoned game but that was a watershed moment, if you pardon the pun.
"There have been a number of games since and both teams knew this one was their game in hand so everybody knew what the three points meant."
The Addicks had already missed a host of chances, with Church firing wide from six yards out inside two minutes and Yann Kermorgant rattling the post, before Stephens opened the scoring with a memorable strike.
Doncaster headed a Cameron Stewart cross out of their penalty area only for Stephens to volley it straight back into the top corner from 20 yards.
And Church made amends for his earlier miss when he ran onto Johnnie Jackson's through-ball and rolled it in off the post with an hour gone.
"We should have scored in the first minute but it needed an outstanding goal to break the deadlock," added Powell.
"It was a great finish by Dale and I'm really pleased for him, he's been playing well.
"But we needed that second goal and it was a composed finish. I'm glad Churchy got the goal as he could have had a hat-trick."
Doncaster boss Paul Dickov refused to dwell on the original postponement, but he was not happy with their performance.
Disappointing Rovers failed to test Charlton keeper Ben Alnwick, who was thrown in for his debut after Ben Hamer was injured in the warm-up.
"It's chalk and cheese," said Dickov. "We had six players missing from the abandoned game.
"But take nothing away from Charlton, they looked half a yard sharper than us.
"It grated at the time maybe but I can't let it now. I'm not going to make excuses, we should have done better than we did.
"In the majority of games this season we have competed well, but not tonight. We didn't match their desire and Charlton wanted it more than us."