"You lie," yelled Wilson, during the speech.
For his outburst, conservative Wilson swiftly apologized to the White House on Wednesday night. On Thursday, facing many cameras, Wilson said his remark was spontaneous and based on conviction.
"People who have come to our country and violated laws, we should not be providing full healthcare services," said Congressman Joe Wilson, R-South Carolina.
Roskam, who was next to Wilson during the speech, said the outburst was out of bounds, but not at all characteristic of his colleague from South Carolina.
"There is a decorum to the House of Representatives. There is an expectation about how the president of the United States should be treated particularly in that setting and I think it's to Congressman Wilson's great regret that he shouted out the way he did," said Wilson.
"I think it was unprecedented," said Prof. Michael Mezey, DePaul University.
Presidential scholar Michael Mezey has spent most of his adult life watching and teaching about Congress and the presidents.
"The Congress functions as it does because members observe these norms of behavior of acting civilly to each other. A breakdown will be detrimental to the institution."
Civility in Congress was not always the order of the day. In pre-Civil War days, one Senator pulled a revolver on another, but didn't shoot. In a bitter, personal fight over slavery, one southern congressman beat a northern senator bloody with his cane.
It was a different time, of course. Even today, in other countries, legislative civility can break down: a Taiwanese parliament food fight began with a debate over a weapons purchase.
Different countries have different protocols to govern civility by the elected. While there are rules, tradition governs most behavior in the U.S. Congress. Wilson's outburst probably won't lead to any sanction, and Mezey doesn't believe it means more of the same in the future.
"But I think we are in a period when people of different ideological viewpoints ability to work together on common problem seems to be deteriorating in the face of advanced partisanship," said Mezey.
Members of Congress - on the floor - address each other through the chairman of the session. That's meant to avoid direct exchanges which could lead to name-calling. So if one congressman on the floor of the House were to turn to another and yell out, "You lie," he or she could face sanctions under House rules.