"I think it's extraordinarily unknowledgeable and unfortunate. I think she recognizes it; she apologized for it," said Romney to Sean Hannity on Fox News Wednesday night.
Rosen later apologized for her remark after President Obama and high-profile members of his campaign moved quickly to denounce the statement.
Republicans painted her remarks as an attack on stay-at-home mothers.
"A lot of folks are home taking care of kids and also working in the day or at night going to another full-time job," said Romney on Wednesday. "It's tough being a mom whether you're working outside the home or not."
He also acknowledged that his wife's struggles have been of a different kind.
"My wife's struggles have not been so much economic as they have been health-wise, and she's a champion, in my view," he added.
Ann Romney told supporters at a private fundraising event on Sunday that the Rosen controversy was an “early birthday present.”
“It was my early birthday present for someone to be critical of me as a mother,” she said. “That was a really defining moment, and I loved it.”
For more on the 2012 GOP race and presidential election, visit GOP12.