Since you are going by just the Bible, I think you need to proceed in the proper order. Here’s the first thing that you need to do: In order to be guided by the Bible alone, you first need to determine which books belong in the Bible; and since the Bible did not float down from heaven leather bound and containing 72 books, you’ll have to find some authoritative way to determine exactly which books are inspired and belong in the Bible.
Since we live in a day when we can go to the store and purchase a book called the Bible that contains 72 books, we just assume that all these books must be Divinely inspired - as if there was a Divinely inspired list of books that accompanied the individual books themselves. that was used in the selection of the 72 books. When we realize that this is not the case, and that the books that make up our Bible are actually just 72 individual books (most of while make no claim of being Divinely inspired), we realize that we need to determine which books REALLY belong in the Bible, and which don’t. That way, we can have a sure guide to follow.
If we skip this first step, we are implicitly trusting that a group of Catholic Bishops were infallible when they chose these 72 books; and if we don’t accept that these Bishops were protected from error when they selected these books, how can we trust the Divine Inspiration of each individual book respectively?
So, the first step is to throw out the list of allegedly inspired books and start from scratch in determining which books are TRULY inspired. Now, how are you going to do this?
The point is, there is an authority outside of the Bible. It is this authority that selected the books that now make up the Bible. If we trust this authority when it selected the books of the Bible, why not trust the same authority when it teaches about the efficacy of reciting the Rosary? And if we use the Bible alone as our guide, we will search in vain to determine, not only which books belong in the Bible, but also how two people go about getting married, or whether or not a man is allowed to marry multiple wives, as was permitted during the Old Testament, and which is not expressly forbidden in the New.
The Bible alone theory is actually dangerous and leads to “as many sects and Creeds as their are heads” to use the words of Martin Luther who came up with this theory in the 16th century. The Bible is the inspired and inherent word of God, useful for instruction and teaching, as it says, but it is not our only authority, and if we try to make it what it is not intended to be it will not serve the purpose we wish. As evidence for this, just look at the 30,000 + Protestant denominations that are divided due to their multiplicity of interpretations of the Bible.
Just as the USA has the Supreme Court, whose job it is to interpret the laws passed by Congress, so too God has left us the hierarchy of the Church to interpret the Bible. The hierarchy of the Church is that divinely instituted guide that helps us to properly understand God’s law as presented in the Bible. That’s why Jesus Himself said that if two people have a dispute they should “take it to the Church”, and that he who refused to hear the Church should be considered “as a heathen an publican” (Mt 18:15-17) If we separate the two (the Bible and the hierarchy), as did the Protestants in the 16th century, we will end in as much confusion as they.
**Now, regarding the Rosary. ** There is more to the Rosary than the Hail Mary, but my guess is that it is the Hail Mary you have a problem with. The first two parts of the Hail Mary are taken directly from the Bible: “Hail Mary full of grace the Lord is with thee” is the salutation of the Angel Gabriel; “Blessed art thou among women and blessed is the fruit of thy womb” is what Elizabeth said when she was “full of the Holy Ghost”. In the last part - “pray for us sinners now and at the hour of our death” - we are simply asking Mary to pray for us, which is similar to asking a friend to pray for us. The difference is that Mary is no longer on earth. Like the other saints in heaven, she is perfect and “sees God face to face”. Since we are told that “the prayers of a righteous man (or women) availeth much”, we can understand how beneficial are prayers of those who are perfect in heaven - much more so than sinners on earth.
But I really think, if you desire to be guided by the “Bible alone”, the first step for you is to determine which books are Divinely inspired so you have a sure guide to follow. Don’t believe that just because some man happened to make a single book containing 72 books, that each and everyone of them is Divinely inspired. Martin Luther himself did not proceed with this presumption, but instead removed those books he didn’t like which is why the Protestant Bible today only has 66 books. When Luther threw out 6 books, 66 remained. Notice that. After removing 6 66 remained. Interesting number, 666. I wonder if this number can be found anywhere in the Bible? :hmmm: