He was born in 1698, near Genova, Italy. When he was 10, he went on a summer holiday to his relatives, a very pious couple. They noted the piety of the youth, and asked permission of his parents to take him to their house in Genova to educate him there. Capuchin priests came often to visit the house of this couple to ask for assistance for the poor. These religious recommended the youth to the Provincial Father. He made arrangements for John to study in Rome. In the Roman College he studied with great application, gaining the liking of his professors and friends. He was ordained a priest at the age of 23.
He read in some exaggerated book that recommended doing very strong penances and he dedicated himself to mortify himself in food, drink, and sleep, so intensely that a nervous depression overtook him that left him incapable of doing anything for several months. He was able to regain his strength, but from then on he always had to struggle against his poor health. He learned that the best mortification is to accept the sufferings and the work of every day, doing well in each moment what one must do and to have patience with the people and the bothers of life.
From the time he was a seminarian, he felt a great predilection for the poor, the sick and the abandoned. The Supreme Pontiff had founded a shelter to receive people that did not have anywhere to spend the night and the young John Batiste went there for many years to care for the poor and the needy, to teach them catechism and to prepare them to receive the Sacraments. He took several friends with him, over whom the work had a great influence. He also agreed to go himself in the early hours of the morning to the market, when the farmers were arriving to sell their produce. There he taught the children and the adults catechism and prepared to make their confession and receive first Communion.
The first years of his priesthood he almost never dared to confess because it seemed to him that he would not be able to give the proper counsel. But one day a holy Bishop asked him to dedicate himself to hearing confessions in his Diocese for a time. There John Batiste discovered that this was the office for which God had destined him. Upon returning to Rome, he told one of his friends, “Before I was asking myself what would be the path for me to achieve heaven and to save many souls. I have discovered that the help that I can give to those that want to be saved is to confess them. The great amount of good that can be done by confession is incredible.”
He went to help a priest in a church that very few people attended. But from the time that Rossi began to confess there, the Church was frequented by hundreds and hundreds of penitents that came to be absolved of their sins. Each penitent brought other people with them to be confessed by him and the conversions that were happening were admirable.
The Supreme Pontiff entrusted to him the office of going to confess and preach to the prisoners in jail and the employees that worked at the prisons. And there he obtained many conversions. They invited from everywhere the sick, prisoners, and people that desired to be converted. He went to many places to preach missions and obtained from heaven numerous conversions. In the hospitals he was an esteemed confessor and consoler of the sick. His friends were always the poor, the helpless, the sick, street children and sinners seeking conversion. He lived for them and he totally spent his life for them. He always remained humble and ready to help as many as possible.
On May 23, 1764, he suffered a heart attack and died at the age of 66. His poverty was such that they had to use alms to pay for his burial. 260 priests, the Archbishop many religious and an immense crowd attended his funeral. The requiem Mass was sung by the Pontifical choir of the Basilica in Rome.