Catholics are free to believe it or not. However, the Rosary is a meditation on the events of the lives of Jesus and Mary. How could that not be "a powerful armor against hell"? What better topic to contemplate?
How can I square the last part of this with the Bible? I offer this Rosary for the purpose of knowing the Truth (?)and obtaining contrition and pardon for my sins(?)
Prayer Before the Rosary
Queen of the Holy Rosary, Thou didst deign to come to Fatima to reveal to the three shepherd children the treasures of grace hidden in the Rosary. Inspire my heart with a sincere love of this devotion, in order that by meditating on the Mysteries of our Redemption which are recalled in it, I may be enriched by its fruits and obtain peace for the world, the conversion of sinners and of Russia, and the graces which I ask of Thee in this Rosary. (Here mention your request.) I ask this for the greater glory of God, for Thine own honor, and for the good of souls, especially for my own. Amen.
I offer this Rosary for the purpose of knowing the Truth and obtaining contrition and pardon for my sins. Amen.
There is no armor there...It fails to teach you even of the smallest wiles of the devil...
Eph 6:11 Put on the whole armour of God, that ye may be able to stand against the wiles of the devil.
Eph 6:17 And take the helmet of salvation, and the sword of the Spirit, which is the word of God:
You absolutely have to have the word of God (sthe scriptures) to know and then fight the wiles of the devil...