While I in absolutely no way assert that the Rosary came from Muslim prayers beads (I do NOT believe they did), if they had come from them, would that be evidence of them being a bad devotion. Much that was pagan has been baptized and brought to Christ so that the fullness of the limited truth given to those outside the Church might be realized.
Heck, does the Catholic Church reject the convert who now confesses Christ and the Truth of the Church He founded? No, once baptized and confirmed, a convert is fully Catholic and accepted as such.
The indigenous people of South and Central America mistakenly worshipped a Maternal God who required human blood sacrifice. After Our Lady of Guadalupe’s visitation near Mexico City, Millions of the Natives converted to Catholicism as they recognized the fullness of the truth in Catholicism that had been incorrectly hinted at in their Pagan faith. The Queen of Heaven, while not a God, is a Queen who loves her children and shares with us the truth of the one sacrifice for all time, that of her Son, who Is God.
Just something to think about. The Pagans follow their religions because there is a small kernal of truth that leads them astray. Once it is rightly compared to the fullness of truth, they come home, sometimes with an appreciation for aspects of the faith that have been neglected by many who have been in the Church before them.
CARose