Standing before a cheering multitude yesterday, Alfonso Robelo, one of five members of Nicaragua's new government junta, looked every inch the triumphant guerrilla.

Bushily bearded, his uncut hair curled over his collar, Robelo wore a black and red kerchief, the colors of the Sandinista National Liberation Front, knotted around his neck. Now that the war against the dictatorship of Anastasio Somoza had been won, he told the crowd, the real revolution of building a new country woulu begin.

Six months ago, a close-cropped, smooth-chinned Robelo sat in the living room of this home in one of Managua's plush upper-class neighborhoods, and spoke of the dangers of a guerilla-run government.

Surrounded by his fashionably dressed wife, his priceless pre-Columbian art collection and the family Pekingese, Robelo said young businessmen and moderate politicians like him were as nervous about a guerrilla victory that might lead to communism as they were opposed to more years of Somoza.

Robelo, 39, is perhaps the best example of the contradictions and compromises that make up Nicaragua's new administration. While the former may become its greatest weakness, it hopes to draw its strength from the latter.

Much like the coalition governments that spanned post-World War Ii Europe, the junta proposes to balance political forces ranging from doctrinaire Marxism to near-reactionary capitalism. While those forces joined for 18 months in the common fight against the Somoza dictatorship, the alliance was often an uncomfortable one whose members can now be expected to vie for power in the new order.

Who will dominate remains to be seen. During 46 years under the Somosas, few other leaders emerged. Opposition politics were largely repressed, businessmen were coopted to accept what profits the Somozas allowed them, and the guerrillas were practically unknown but feared as extremists.

But it was the Sandinistas who won the war, and those who did not jump on their bandwagon in time now find themselves left behind.

Toward the end it was largely the politicians who got cold feet, with some cooperating in unsuccessful attempts by the United States and some Latin American governments to ensure a conservative majority in the new government.

Accordingly, the Conservative Party, the traditional and ineffectual opposition to the Somozas, and other small conservative groups have little place in the new administration.

Private business was more supportive, and fared better. Among the new government's Cabinet and adminstrative officials are some of Nicaragua's most prominent businessmen and professionals.

The bulk of the Cabinet, however, is made up of members of the Group of Twelve, an organization of liberal church, business and academic leaders who were early supporters of the rebels.

The guerrillas themselves are presented in the Cabinet only by Cultural Minister Ernesto Cardenal, a Jesuit priest and Sandinista spokesman for the past two years, and Interior Minister Thomas Borge, leader of the Prolonged Popular War faction of the Sandinistas.

That and the Proletarians are considered the most radical of the three factions making no bones about their plans to install socialism eventually in Nicaragua and until then letting the country evolve to the left.

One of the best-known names among the Sandinistas, Eden Pastora, known as Commander Zero, has not been given a place in the leadership but will remain in the army. Pastora led the assault on the National Assembly building almost a year ago that launched the first phase of the civil war. Although well known, he is not a major political force.

A key to how far left Nicaragua will go is how much influence Sandinista militants have over the junta. So far, the junta program is vaguely social democratic, combining familiar Latin American liberal policies - including a modest plan of land reform similar to that of Chile's Eduardo Frei in the 1960s and a mixed state and private economy along the lines of Jamaica under Michael Manley.

Several of the junta members are little known and must emerge from the shadow of the idolized Sandinista heroes. They also must learn to avoid the pitfalls encountered by other governments by committee.

Robelo, despite his new guerrilla image, is believed to be the most conservative of the five junta members. A chemical engineer trained at New York's Rensselaer Polytechnic Institute, he has three young daughters and belongs to a wealthy family from which he inherited a profitable vegetable oil business.

In 1975, Robelo became president of the Nicaraguan Development Institute and a prominent business spokesman. He came to the forefront of political opposition in 1978 when he organized a two-week strike against Somoza and formed the Nicaraguan Democratic Movement of young liberal businessmen.

He brought that organization into the Broad Opposition Front that negotiated with the Somoza government through the United States following fighting last September. Considered a frontrunner on a U.S. list of candidated to replace Somoza at that time, Robelo long vacillated between his eagerness to please the Americans and his desire to impress the Sandinistas as militantly anti-Somoza.

Although his appointment to the junta was viewed as a concession to left-center capitalists, Robelo took the hard line against U.S. attempts to influence the junta during negotiations over the past month. He has been the principal junta spokesman on economic matters.

Another surprising hard liner in resisting U.S. pressure was Violeta Chamorro, 49, the widow of opposition newspaper publisher Pedro Joaquin Chamorro and mother of four growth children.

Until her husband's death, Mrs. Chamorro was known primarily as the wife of one of Anastasio Somoza's most prominent political foes. When Chamorro was murdered by unknown assailants in January 1978, she took up not only his political banner, becoming a sort of matriarchal symbol to the moderate opposition, but also an active participant in the family - owned newspaper La Prensa.

As was her husband, she is a close friend of former Venezuelan president Carlos Andres Perez, whose government provided moral and material support to the Sandinistas.

She is the most retiring member of the junta and seldom addresses substantive policy issues at press conferences or public gatherings. Rather, she speaks generally of Nicaragua nationalism and liberal democracy and is considered the representative of those who followed her husband's moderate political line.

Sergio Ramirez, a 37-year-old attorney and author, has emerged as the informal leader of the junta and its political pivot.

Tall, dark and soft - spoken, Ramirez projects an attitude of calm, reflective cynicism. Throughout the struggle against Somoza, while others allowed themselves to plunge into despair or enjoy moments of ecstasy, he remained unexcitable and quietly determined.

Ramirez has spent most of his adult life outside the country and is barely known as a political figure in Nicaragua. The son of middle - class parents who were supporters of Somoza's Liberal Party, he studied law at the National University, where he joined a student political group.

Until he became involved in politics in 1977, Ramirez taught and studied in the United States and West Germany and wrote. His best - known novel, "Splendid Times," is a sociological view of early 20th century Nicaragua.

Ramirez also wrote a biography of Augusto Cesar Sandino, the 1920s Nicaraguan guerrilla hero from whom the Sandinistas take their name. He was one of the founding members of the Group of Twelve in 1977.

Considered a social democrat, Ramirez is nevertheless one of the few non - guerrillas trusted by all three Sandinista factions.

On the other side of the junta's political spectrum is Daniel Ortega, 34, the group's only official Sandinista. A member of the nine - man guerrilla directorate, he and his brother Humberto joined the Sandinista National Liberation front as teen-agers when it was founded in the early 1960s.

Since then, he has spent his life fighting the Somoza government or in its prisons. Captured by the National Guard in 1967, he was released in 1974 in exchange for hostages from a guerrilla raid and flown to Cuba. There he trained and returned to Nicaragua clandestinely to try to mediate ideological battles between bickering Sandinista factions.

The Ortegas formed a new guerrilla faction that became the largest of the three. Called the Insurrectionalists, they have strong alliances with Nicaragua's liberal political and business groups.

The Insurrectionalists generally are less doctrinaire than the other two guerrilla factions.

Daniel Ortega is considered a main Sandinista military strategist and political analyst and was a commander on the southern front during the civil war.

Perhaps the least - known figure in the junta is Moises Hassan, 37, a civil engineer with a doctorate in physics from the University of North Carolina.

Hassan is the son of a Nicaraguan mother and Palestinian father.

Until he became active in the anti - Somoza battle last year, he was the dean of the National University's College of Science and Letters. As head of the activist National Association of Professors, Hassan became its delegate to the United People's Movement, a Sandinista political arm founded last year.

"I am not a Marxist," he said in a recent interview. "I am a socialist, and I believe eventually we should have some kind of socialism here, adapted to the Nicaraguan situation." CAPTION: Picture, Three of Nicaragua's new leaders last year, from left: Sergio Raminez, informal junta head, Education Minister Carlos Tunnermann, Foreign Minister Miguel d'Escoto. By Karen DeYoung - The Washington Post