Ireland face England at Twickenham on Saturday and the legendary centre will win his 139th international cap - eight of which came for the Lions - equalling the record set by Australian scrum-half George Gregan.
Rowntree is part of the England camp that will look to ruin O'Driscoll's big day on Saturday, but the former Lions prop has nothing but great admiration for the 35-year-old.
"Beating us will mean everything to him," said Rowntree. "What a player - he's an icon.
"He's a thoroughly professional player and I really enjoyed working with him. As a man he's exceptional.
"You hear the way Owen Farrell, Luther Burrell and Billy Vunipola speak about him, you can tell the respect they have for him."