Christianity, that is the gospel of reconciliation of sinners to God through Jesus Christ, was invented by God himself before the foundation of the world. As of course, were all Christian people (and all other people) whom God created and determined their lives, thoughts, actions and ends. This gospel of Jesus Christ was first revealed to Adam and Eve in the garden of Eden after they had fallen by sin, in the promise that one day the "seed of the woman" would "crush the serpent's head". Since that time, all those who obeyed God and put their hope in this promise of salvaiton in Christ deserve the title "Christian", including father Abraham, of whom Jesus said, "He saw my day and rejoiced in it."
As far as the Church of Rome, it was once a true Church of Jesus Christ, but is now held captive by a renegade line of Roman bishops who have proclaimed themselves head of the universal church instead of Christ. They hold the people in bondage, teaching them false doctrine and deceiving millions. This is that tyrant whom it is said, "the Lord shall destroy [him] with the brightness of his coming." 2 Thessalonians 2:8
Genesis 3:15, John 8:56, 2 Thessalonians 2:8