“Where does it say it is the Roman tradition, that teaches that Paul was all wrong about salvation by grace, and that we needed the Roman Church, 400 to 500 years after the fact, to set us straight?”
Let me correct you since it would be wrong to allow you to continue in such errors:
1) The Catholic Church has always taught salvation by grace alone - just as St. Paul did.
2) The Catholic Church was founded by Christ. The Roman Church is merely the leading Church in it. There are 22 churches in the Catholic Church.
3) The Catholic Church was founded by Christ not 400 or 500 years after His ascension but when He was on earth with the Apostles.
“1) The Catholic Church has always taught salvation by grace alone - just as St. Paul did.”
“...the Second Vatican Council confirms: ‘The bishops, successors of the apostles, receive from the Lord . . . the mission of teaching all peoples, and of preaching the Gospel to every creature, so that all men may attain salvation through faith, Baptism and the observance of the Commandments,’” (CCC 2068).
The specific precepts of the natural law, because their observance, demanded by the Creator, is necessary for salvation, (CCC, par. 2010).
If any one saith, that the justice [righteousness] received is not preserved and also increased before God through good works; but that the said works are merely the fruits and signs of Justification obtained, but not a cause of the increase thereof; let him be anathema.” (Council of Trent, Canons on Justification, Canon 24).
What saith the scripture?
Eph_2:8 For by grace are ye saved through faith; and that not of yourselves: it is the gift of God:
“The Catholic Church was founded by Christ not 400 or 500 years after His ascension but when He was on earth with the Apostles.”
The Rock upon which the church is built is the confession of Jesus Christ. All Christians are stones, and priests and saints of the true church, which is Christs body, with Christ as the chief cornerstone.
1Pe 2:5-6 Ye also, as lively stones, are built up a spiritual house, an holy priesthood, to offer up spiritual sacrifices, acceptable to God by Jesus Christ. (6) Wherefore also it is contained in the scripture, Behold, I lay in Sion a chief corner stone, elect, precious: and he that believeth on him shall not be confounded.
Peter never, in any of his epistles, calls himself the Rock upon which the church is built, or refers to himself as anything more than an Apostle of Jesus Christ, just as Paul and the others called themselves. In fact, Paul even rebuked Peter when he was in error. Not as an inferior having respect for a Pope, but as an equal.
Gal 2:11 But when Peter was come to Antioch, I withstood him to the face, because he was to be blamed.
This doctrine of Papal primacy, universal Bishop as the head of the church, is one that came later.
Ignatius, writing sometime before his death between 97 and 115AD, listed the highest tier of the church as the Bishop. He never mentions any higher tiers.
Pope Gregory the first, more than 400 years later, who asserted Peter was the First of the Apostles, nevertheless denied the title of the Universal Bishop (though the one who came right after him petitioned the Emperor that he should take the title), and asserted that the See of Peter was made up of three locations.
But I confidently say, that whosoever calls himself universal bishop, or desires to be called so, in his pride is the forerunner of antichrist, because in his pride he prefers himself to the rest. And he is conducted to error with a similar pride; for as that wicked one wishes to appear a God above all men, so whosoever he is who alone desires to be called a bishop, extols himself above all other bishops. To Mauritius Augustus.
St. Peters Primacy descended to three Bishopricks, Alexandria, Antioch, and Rome.
Whereas there were many apostles, yet for the principality itself, one only see of the apostles prevailed, in authority, which is of one, but in three places. For he elevated the see in which he condescended to rest, and to finish his present life. He decorated the see, to which he sent his disciple the evangelist, and he established the see, in which, although he intended to leave it, he sat for seven years. Since there fore the see is of one and is one, over which three bishops preside by divine authority, whatsoever good I hear of you, I ascribe to myself. And if you hear any good of me, number it among your merits, be- cause we are all one in him who says, that all should be one, as thou, O Father, art in me, and I in thee, that they may be one in us. In the Eulogy to the Bishop of Alexandria
Theodoret references the same belief when he places the throne of Peter under the Bishop of Antioch:
Dioscorus, however, refuses to abide by these decisions; he is turning the See of the blessed Mark upside down; and these things he does though he perfectly well knows that the Antiochene (of Antioch) metropolis possesses the throne of the great Peter, who was teacher of the blessed Mark, and first and coryphæus (head of the choir) of the chorus of the apostles. Theodoret - Letter LXXXVI - To Flavianus, Bishop of Constantinople.