Yes, and these men all were Catholic Christians.
The NT scriptures existed before the Roman church
Before the Catholic Church founded its Roman local Church? Possibly, but that is not the point. The Catohlic Church was established by Christ in the Upper Room with the descent of the Holy Spirit on the Apostles. "Rome" has little to do with it.
the ASSUMPTION that the "church" of the NT is today the Roman Catholic church
It is an assumption that can be proven and in fact has been proven. Whatever changes that happened between the time the New Testament was written and the Church today are perhaps refinement and firther explanation of the Faith, but the Catohlic Church today professes the faith of the Apostles, as we can see from the Hoyl Scripture. This is in contrast to the inventions done by Luther in direct contradiction of the Scripture. Every time I ask where does the Catholic Church today contradict the scripture I get fluffy nonsense like "meat on Friday" -- something that does not pertain to the dogmas of the faith itself. That is because while there is much the Church taught the world that is not in the scripture, there is nothing that is in the scripture that the Church disagrees with. The Church is the inspired human author of the New Testament and the inspired final editor and exegete of the Old Testament.
To annalex in regard to your three points made in response, respectively:
1) No, not in the sense you mean.
2) Piffle. The church of the firstborn, the children of God, the followers of the woman’s Seed, has existed since the fall into sin. If you want to say the Catholic Church was established in the upper room, go ahead, since what you are referring to is the outward structure of “church.” But that is not what Christ established in the upper room. There He put the last piece in place for the church of the fulfillment of the OT, that is, the church of the NT, which as Revelation and other places show, is one in faith with the church of the OT. On this point all 24 elders agree (said a little tongue in cheek, perhaps, but not much). He established nothing more, but surely nothing less!!!!!!!!!!!!!!!!!!
3) No. Simply, no.