Trailing 1-0 in the 60th minute, Paulo Nagamura got the equalizer for Kansas City, notching his first of the year when he fired in an attempted clearing header by Toronto defender Jeremy Hall.
Then, 17 minutes later, Chance Myers found Rosell in the penalty area and he rolled a shot past goalkeeper Freddy Hall for the game-winner.
For Eastern Conference-leading Kansas City (15-7-5) it was the fifth straight match without a loss.
Ryan Johnson scored for the Reds (5-16-6).
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