Last week the press reports said Rosalynn Carter, touring Latin America as her husband's personal envoy, had decided - after a phone consultation with the President - to see two American missionaries who had been jailed in Brazil.

The First Lady was clearly miffed by the reports, and she sent her aides to set the record straight: she had made the decision herself; she told Carter what she planned to do; and he said okay.

The incident demonstrates the determination of Mrs. Carter to make clear from the beginning of her two-week 12,000-mile odyssey through seven countries until it ended Sunday that the journey was her show and that she alone was running it.

What really happened, her aides said afterward, was that the missionaries, Thomas Capuano and the Rev. Lawrence Rosebaugh, came to the America consulate in Recife, a north-eastern Brazilian city, and said they wanted to see Mrs. Carter when she arrived the next day.

The U.S. consul, Marvin Hoffenberg, then telephoned U.S. Ambassador John H. Crimmins, who was with Mrs. Carter in Brasilia. Crimmins relayed the missionaries' message, and she said at once she wanted to see them and hear their story begin beaten, stripped and jailed for three days in May until U.S. authorities secured their release.

That night Mrs. Carter received a call from her husband, and when he heard that she wanted to meet the missionaries, he said he thought it was a good idea.

He could have veoted it, of course and the talk was in a sense a consultation, but Mrs. Carter's aides said the press reports had missed the point that the initiative was hers.

In the early days of her tour, when she was in Jamaica, Costa Rica and Ecuador, she relied on her staff to carry a good part of the conversation with the leaders of those nations.

But as she gained confidence, she took over more and more of the talk from the U.S. aide, and by the time she got to Lima, she announced that she had handled the three-hour discussion with Peruvian President Francisco Morales Bermudez herself and that only one question had come from her staff.

Throughout the trip she faced the underlying question of how much of it was a goodwill tea party and how much was serious talk on important subjects. Her goal was to stress the latter, which clearly surprised the foreign leaders even though the State Department had been telling them for weeks that was her intention.

Daniel Oduber, president of Costa Rica, was so overwhelmed that he insisted her visit was "very important because for us it's exactly the same as if President Carter had arrived and made personal contact himself."

The other Latin American leaders she saw were not that effusive, but by any standard the reviews were good:

Carlos Andres Perez, president of Venezuela, called her "an extraordinary woman," acknowledged that protocol required him to say polite things, then added, "but believe me, I'm very sincere when I say I was surprised, very pleasantly surprised, by her knowledge and her frankness."

Jose de la Puente, Peru's foreign minister, said she was 'much better informed than I had thought - far more direct. She is the perfect ambassador between the United States and Latin America."

And even in Brazil, which has had chilly relations with the United States and where some sectors of the Press questioned whether she would be any match for their experienced diplomats, Foreign Minister Antonio Azeredo da Silveira commented grudgingly, "I answered with some frankness questions I wouldn't have if she hadn't brought up the subjects."

The subjects were tricky, and how well the First Lady handled them will take time to evaluate. SHe discussed ways the United States might help Jamaica get loans more easily from international banks. She listened to Costa Rican pleas for increased beef imports into the United States and said bluntly that her husband could make no promises.

She heard Ecuador's request for modern aircraft and expressed sympathy with its faers of Peru. She told the Peruvians they should stop their frantic arms buildup and spend the money instead on social and economic programs.

She told the Brazilians they should seek alternatives to building a nuclear reprocessing plant, and she backed up the U.S. commitment to human rights with symbolic gestures besides seeing the missionaries - a visit to the Brazilian Congress and Supreme Court, both of which have been hobbled by the military dictatorship, and a brief meeting with leaders of the opposition party in the Congress.

Perhaps the most dramatic symbolic gesture in the long run will turn out to be Rosalynn Carter's declaration to about 250 peruvian dignitaries: "Sellama Peru Mellama Peru tambien."

It means, "You are Peru. I am Peru also." When she said it, the Peruvians cheered and applauded, and one said later he had tears in his eyes.

A U.S. official traveling with her said the comment had wider meaning: "We were saying to Latin America, 'We stand with you. We are about you. We want closer relations."

The idea for the trip came in early April when Carter was working on his latin American policy speech to the Organization of American States.

"I really don't know who suggested the trip," Mrs. Carter said last week. "It just happened. He said, "Maybe you should go,' or I said. 'I'd like to go.' Jimmy said all during the campaign that he was going to send his family on trips around the world, theat he would use his family as a surrogate."

To prepare herself, the First Lady studied Spanish and listened to 40 experts on Latin America in 13 sessions of two to five hours each. On the trip she got up at 5:30 every morning, read reports on the country she was visiting, and called in State Department and National Security Council aides for more briefings.

The formidable single-mindedness and devotion to the work ethic began to show results. In the early part of the trip she had appeared frail and at times tremulous as she spoke in public, but by the time she reached Ecuador she was handling news conferences like a veteran.

At the end of the trip, a reporter commented that her mission was "unprecedented" for an American woman and asked Mrs. Carter if she saw any significance in the role she was taking.

"If it has not been done before, maybe it's significant," she replied. "I don't know. I've always worked. I worked in a peanut warehouse, and I didn't think about being a woman working in a peanut warehouse. I campaigned for Jimmy. I campaigned because we didn't have any money, and everyone in my family had to go and campaign. I'm doing this because I really think it can be helpful to Jimmy." She paused and added, "I'm glad I'm a woman."