Ronaldo's sparkling display and brilliant goal earned him only rebukes from Roma players and officials, who branded him disrespectful with his tricks.
But Ferguson said: "The most important message Cristiano is giving out is that he is a great player who is not afraid to take the ball and beat a man.
"In this modern day it's a breath of fresh air and he will not be afraid to do it.
"That is what people pay to see. Perhaps it annoys opponents he is prepared to take the ball to them."
Roma, as many other teams have done, tried unsuccessfully to kick, barge and elbow Ronaldo, 23, out of the game.
But Ferguson has a warning for them - and any Middlesbrough player who might fancy trying it tomorrow in the league clash at the Riverside.
He insisted: "Ronaldo is a winner. They cannot kick him out of the game.
"He will always get up and carry on playing.
"It will not worry him if Roma come looking for him in the second leg."