When President Reagan walked into the Roosevelt Room of the White House to meet with antiabortion leaders yesterday, he carried a videocassette of "The Silent Scream," a documentary of a first-trimester suction abortion narrated by a former clinic chief turned antiabortionist.

"He [the president] had read the transcript. He said he was going to watch it in the next day or two and thought everyone in Congress should see it," said Joseph M. Scheidler, head of the Chicago-based Pro-Life Action League, who was present. Rep. Robert K. Dornan (R-Calif.), who was also there, said this "incredible film" used modern photography techniques to show "a young child fighting for its life inside his mother's womb as an abortionist doctor begins to tear it apart."

Eighteen million "preborn babies" have been destroyed in a "Nazi death toll" in America in the 12 years since the Supreme Court ruled that women have a constitutional right to choose abortion, Dornan said in an address last night before the third annual Rose Dinner of the March for Life Education and Defense Fund. A red rose is the symbol of the organization, which honored Dornan with its Life Award for pushing antiabortion legislation.

Dornan strongly condemned bombings of abortion clinics across the nation, saying violence may cause injuries and work against the movement. "The wind is in our sails," he declared. ". . . There's joy on our side! The main motive force of our movement is love."

The dinner for 350 was held at the Departmental Auditorium on Constitution Avenue after a March for Life from the Ellipse to the Supreme Court attracted 71,500.

Like "The Silent Scream," much of last night's rhetoric focused on the physical and psychological realities of abortion. It was strong stuff.

"Oh God, we come to you in the midst of death," said Canon John W. Howe, president of the National Organization of Episcopalians for Life, in his opening prayer. "We come to you on behalf of the unwanted, the imperfect, the poor, the distressed and the unborn."

Inside the womb, said Sen. Gordon J. Humphrey (R-N.H.) in his address, is "not a blob, but -- surprise! -- a tiny human being."

He referred to the little gold baby feet worn on the lapels of many there -- another symbol of the group.

"A nation that's murdered 18 million children is in bad shape," said Scheidler, once a press aide to the late Chicago mayor Richard Daley. "We're taking 4,500 lives a day, live human beings with feelings and blood coursing through their veins, and they cut their legs off. They don't even give them an anesthetic. You wouldn't do it to a dog!"

"You can see the pain, the look of agony on the child's face as the abortion is being performed," said Catholic University law student Susan Juroe of an abortion film she saw.

Scheidler was trying to raise bail money for antiabortionist students jailed yesterday while demonstrating at the Supreme Court. He said Nellie Gray, president of March for Life, refused to make an announcement at the dinner asking for contributions -- and indeed, no announcement was made.

In a skit presented by the Sounds of Liberty, a group from Liberty Baptist College in Lynchburg, the group sang: Little life is the start of all the life there is. When we take little life, it's a sign that we're about to fall.

Charles Onofrio, an attorney from Colorado who helped draft that state's law against spending state money on abortion, received an award last night, as did two students for their antiabortion essays and poems.

Winner Lea Pannella of Hamden, Conn., wrote in her essay: "Americans condemned Hitler because he encouraged the killing of . . . Jews, Gypsies and non-Aryan races -- those he considered not fully human. Now the Supreme Court defends what the Nazis did by passing laws that permit abortion which declares the fetus sub-human."

And Trish Keller of Dickinson, N.D., won with a poem that said in part: The Lord gave each of us a chance To live, to love, to sing, to dance . . . If euthanasia creeps in as abortion did Then lovely old people society would rid.