Answer: Tradition does hold that St. Dominic devised the rosary as we know it. Saint Dominic is said to have experienced an apparition of Blessed Mother Mary while in a coma, during which he received inspiration to develop the Rosary prayer. Pope Leo XIII, in his encyclical Octobri mense, teaches that the Rosary does in fact have its origin from the Immaculate Mary herself 'by her command and counsel' to Saint Dominic.

For further details see:
Fr. William Saunders, The History of the Rosary
https://www.catholiceducation.org/en/culture/catholic-contributions/the-history-of-the-rosary.html#:~:text=During%20the%2016th%20century%2C%20the%20structure%20of%20the,1221%29%20devised%20the%20rosary%20as%20we%20know%20it.

Taylor Marshall, How Mary Gave the Rosary to St Dominic
https://taylormarshall.com/2011/06/how-mary-gave-rosary-to-st-dominic.html

Taylor Marshall, Did the Virgin Mary Give the Rosary to St Domini
https://taylormarshall.com/2016/08/did-the-virgin-mary-give-the-rosary-to-st-dominic.html

      
St. Dominic de Guzman, Scott # 509-512 (1971)