The Catholic Church wrote the New Testament

Lutero: 

What Scriptures did Jesus point the people to when He was teaching the Roman Catholic Traditions for them to learn?

The Old Testament. The Catholic Church wrote the New Testament based upon the Teachings of Jesus Christ. The New Testament did not exist when Jesus was preaching. Nor did Jesus write it.

And for contexts sake, you need to keep in mind that Jesus ministry caused major controversy among the Jewish religious leaders. Jesus' teachings and practices collided with their "traditions",

That is right. The Traditions which Jesus Christ taught collided with the traditions of the Jews. 

which just like Roman Catholics, they considered their treasured "Tradtions" an expression of God's will.

Jewish traditions were an expression of God's will in the Old Testament.
Deuteronomy 6:7

King James Version (KJV)
7 And thou shalt teach them diligently unto thy children, and shalt talk of them when thou sittest in thine house, and when thou walkest by the way, and when thou liest down, and when thou risest up.

But Jesus Christ fulfilled those, brought them to a close 

Colossians 2:14

King James Version (KJV)
14 Blotting out the handwriting of ordinances that was against us, which was contrary to us, and took it out of the way, nailing it to his cross;


and established His own which we now keep:

2 Thessalonians 2:15

King James Version (KJV)
15 Therefore, brethren, stand fast, and hold the traditions which ye have been taught, whether by word, or our epistle.