Cesare de Rossi was born to a Venetian family in the kingdom of Naples. He was educated by the local Conventual Franciscans and then by his uncle in the College of Saint Mark in Venice. He was both a brilliant military tactician as well as a peacemaker.

At age 16, he became a Capuchin Franciscan in Verona and took the name Lawrence. He pursued higher studies in theology, philosophy, and Scripture at the University of Padua. There he demonstrated an incredible gift for languages--Greek, Hebrew, German, Bohemian, French, and Spanish--and excelled at Bible studies. He gave a Lenten course of sermons while still a deacon, and after being ordained, he preached successfully in Padua, Verona, Vicenza, and elsewhere in northern Italy.

In 1596, he became a definitor general of the order in Rome, a position he was to hold five times. Pope Clement VIII commissioned him to evangelize the Jews; his facility with Hebrew contributed to his success at this task. He accompanied Blessed Benedict of Urbino to Germany to establish the Capuchins as a means of counteracting the spread of Lutheranism. They nursed plague victims and established monasteries at Prague, Vienna, and Gorizia, which were to develop into the provinces of Bohemia, Austria, and Styria. Lawrence then was elected minister general of the Capuchins.

During this time, the Turks were threatening to conquer Hungary. Emperor Rudolf II begged Lawrence to unite the German princes against them. As a result of his efforts, an army was mustered, and he was appointed chaplain general. Before the battle of Szekes-Fehervar in 1601, the generals consulted him on strategy. He advised an attack, rallied the troops, and rode before the army with a crucifix. The victory of Szekes-Fehervar was attributed to him.

In 1602, he was elected vicar general of the Capuchins but refused re-election in 1605. The emperor later commissioned Lawrence to persuade Philip III of Spain to join the Catholic League, and in the course of this task, he founded a house of Capuchins in Madrid. He was then sent to Munich as nuncio of the Holy See at the court of Maximilian of Bavaria, head of the League, from which location, in addition to his other duties, he administered two provinces of his order.

After serving as a diplomat for two more royal tangles, returned to the monastery of Caserta in 1618, desiring a more solitary life. Representatives from Naples came to him, however, and asked him to intercede for them with King Philip about the Spanish viceroy, the duke of Osuna, whose dictatorial methods they feared would cause a rebellion.

Although he was ill and tired and predicted that he would not return alive, he agreed. He was forced to travel to Lisbon in the heat of summer. There he convinced the king of the seriousness of the case, and the duke was recalled. After accomplishing his aim, he returned to his lodging and died on his sixtieth birthday. Lawrence was buried in the cemetery of Poor Clares at Villafranca.

His written works included some controversial pieces against the Lutherans and a commentary on Genesis, but his main contributions are in the nine volumes of his sermons (Attwater, Benedictines, Bentley, Delaney, Encyclopedia, Farmer, Walsh, White).