From the writings of St. Louis de Montfort (1673-1716):
The Holy Sacrifice of the Mass gives boundless honor to the Most Blessed Trinity because it represents the passion of Jesus Christ and because through the Mass we offer God the merits of Our Lord’s obedience, of His sufferings and of His Precious Blood. The whole of the heavenly court also receives an accidental joy from the Mass. Several doctors of the Church — together with Saint Thomas Aquinas — tell us that, for the same reason, all the blessed in Heaven rejoice in the Communion of the faithful because the Blessed Sacrament is a memorial of the passion and death of Jesus Christ, and that by means of it men share in its fruits and work out their salvation.
Now, the Holy Rosary, recited together with meditation on the sacred mysteries is a sacrifice of praise to God to thank Him for the great grace of our redemption. It is also a holy reminder of the sufferings, death and glory of Jesus Christ. It is therefore true that the Rosary gives glory, gives an accidental joy to Our Lord, to Our Lady and to all the blessed because they cannot desire anything greater or more contributive to our eternal happiness than to see us engaged in a practice which is so glorious for Our Lord and so salutary for ourselves.
— The Secret of the Rosary