There is a perception that first ladies are somehow above the political fray, that they often get higher approval ratings than their spouses and are less divisive.
The perception is wrong, said Roberts.
"First ladies are good at campaigning," she said. "They bring a humanity to the candidate, particularly candidates like Barack Obama, who are cerebral and very smart and can talk about political theory at great length. But that doesn't do it for someone who is out of a job or whose child can't afford to pay their student loans."
Roberts pointed to the political role that Laura Bush played as first lady.
The perception that she was the nice librarian, when in fact she was the only first lady to go to the press room and speak at the podium and call for the overthrow of the Burmese government. Hardly pouring tea," said Roberts.