Looking into the history there are different views about the origin and the growth of this devotion. According to tradition, the concept of the rosary was given to Saint Dominic in an apparition by the Virgin Mary in the year 1214 in the church of Prouille. This Marian apparition received the title of Our Lady of the Rosary.
In the 15th century it was promoted by Alanus de Rupe a learned Dominican priest and theologian, who established the “15 rosary promises”.
The practice of meditation during the praying of the Hail Marys is attributed to Dominic of Prussia (1382–1460), a Carthusian monk, who called it “Life of Jesus Rosary”. The German monk from Trier added a sentence to each of the 50 Hail Marys, using quotes from scriptures. In 1569, the papal bull Consueverunt Romani Pontifices by the Dominican Pope Pius V officially established the devotion to the rosary in the Catholic Church.
From the 16th to the early 20th century, the structure of the rosary remained essentially unchanged. There were 15 mysteries, one for each of the 15 decades. In the 20th century the addition of the Fatima Prayer to the end of each decade became more common. There were no other changes until 2002 when John Paul II instituted five optional new Luminous Mysteries. (Rf. http://en.wikipedia.org/wiki/Rosary)
Rosary was the favorite prayer of our father and founder Don Boso. Don Bosco used to say I learnt to recite the Rosary on the knees of my mother. He was very particular that the Rosary should be recited in all his houses.
Today Rosary remains as a simple and favorite prayer of every Christian with its power to strengthen faith and foster a life of virtue.