Again; this is what YOU'D say.
What is the Official Roman Catholic stance on it?
Is the BELEIVE in transubstanciation a a REQUIREMENT for SALVATION or not?
If you do not believe in the Sacrament of the Eucharist as the Church lays it out, then you seriously at odds with Scripture, Jesus’ words and Church’s teachings and your soul is imperilled.
That brings you outside of the Church and its teachings. Not where we are Christians are instructed to go. Does that mean that you will go to hell? That’s up to Jesus at the Judgement. The Church does not teach outside of its authority.
Transubstantiation is merely a device used to explain in somewhat human terms the eternal and unknowable mystery that is the Eucharist. We have only the words of Jesus in the Gospel of John and the traditional belief in the Real Presence which has been shown to exist from the beginning in Paul’s epistles and in the writings and exegesis of early Church Fathers.
That Jesus clearly says one must eat His flesh and drink His blood to have live within them is the basis for this belief. Even when Jesus was present and gave this teaching, those with Him understood what He meant and some rejected Him for it and others remained with Him though they did not fully grasp how He would do this. Jesus knew that as much as could be known would come to His followers under the guidance of the Holy Spirit. He affirms this in
John 14:25-26 “I have said these things to you while I am still with you. But the Advocate, the Holy Spirit, whom the Father will send in my name, will teach you everything and remind of all that I have said to you.”
And again
John 16:12-14 “I still have many things to say to you, but you cannot bear them now. When the Spirit of truth comes, he will guide you into all the truth; for he will not speak on his won, but will speak whatever he hears, and he will declare to the things that are to come.”
What must never be forgotten is that salvation is not possible without Jesus. It is by His grace that we may even dare to hope for eternal life. So, in this light, salvation comes by grace alone.