You, like so many others have so terribly misinterpreted those verses. What those verses say, in fact, is that the result of Jesus' obedience set aside completely whatever the result of Adam's disobedience might have been. So many want to read the first part of those verses and interpret them as the statement of original sin universally for all men. And that is perfectly acceptable. Except of course, the second half of each of those sentences says that Jesus' death on the cross set that aside, universally, for all men. Now please note that it says nothing about our sin; it is talking only about Adam's sin and the effect thereof. You will admit that the original sin imposed by Adam's disobedience was [or would have been] imposed upon all men at birth; therefore what Jesus death on the cross accomplished, among other things, was the imposition of "original grace" upon all men at birth. It undid any effect upon mankind due to Adam's sin. That is the message of those eight verses.
Then of course we must talk about the effect of Jesus' obedience upon mankind due to each one's own sins. That Paul begins to speak about in the very next chapter, beginning actually with verse 20 of chapter 5.
But Roman s 5:12-19 is not about each individual's sins, it is about Adam's sin. Roman's 5:12-19 says there is no such thing as original sin. There would have been had it not been for Jesus. But as verses 12-19 say Jesus' obedience countermanded all that Adam did. Jesus' obedience revoked Adam's disobedience. Original sin was rescinded. And of course it was retroactive to all who lived before Jesus died, just as His death was a ransom for all of mankind even those who lived before Jesus died.
I know precisely what those Scriptures mean and I thank God that I don't agree with you. Romans Chapter Five is indeed about original sin and how only God's provision, the Second Adam, was able to reconcile mankind. You will be in the same category of those Pharisees who denied Jesus as He had been revealed to them in the Scriptures. In John Chapter Five Jesus told the Jewish leaders that Moses had revealed Him to them. One who questions what is stated about Jesus in Genesis is not able to understand who Jesus is from Romans Chapter Five. Science or intellectualism won't save anyone who must stand before the Father without Christ as their attorney.
You are describing a legal system. The legal system never worked and the legal system had one purpose: condemnation, not reconciliation. You have your eyes and mind on what you do and what your intellect imagines, and you are not relying on what Christ has done for everyone, including you. Right now you are rejecting what He has done.
We have a better Covenant now. It's time that you catch up instead of staying dependent upon the Law.
Heb 7:1 For this Melchizedek, king of Salem, priest of the Most High God, met Abraham returning from the slaughter of the kings and blessed him,
Heb 7:2 and to him Abraham apportioned a tenth part of everything. He is first, by translation of his name, king of righteousness, and then he is also king of Salem, that is, king of peace.
Heb 7:3 He is without father or mother or genealogy, having neither beginning of days nor end of life, but resembling the Son of God he continues a priest forever.
Heb 7:4 See how great this man was to whom Abraham the patriarch gave a tenth of the spoils!
Heb 7:5 And those descendants of Levi who receive the priestly office have a commandment in the law to take tithes from the people, that is, from their brothers, though these also are descended from Abraham.
Heb 7:6 But this man who does not have his descent from them received tithes from Abraham and blessed him who had the promises.
Heb 7:7 It is beyond dispute that the inferior is blessed by the superior.
Heb 7:8 In the one case tithes are received by mortal men, but in the other case, by one of whom it is testified that he lives.
Heb 7:9 One might even say that Levi himself, who receives tithes, paid tithes through Abraham,
Heb 7:10 for he was still in the loins of his ancestor when Melchizedek met him.
Jesus Compared to Melchizedek
Heb 7:11 Now if perfection had been attainable through the Levitical priesthood (for under it the people received the law), what further need would there have been for another priest to arise after the order of Melchizedek, rather than one named after the order of Aaron?
Heb 7:12 For when there is a change in the priesthood, there is necessarily a change in the law as well.
Heb 7:13 For the one of whom these things are spoken belonged to another tribe, from which no one has ever served at the altar.
Heb 7:14 For it is evident that our Lord was descended from Judah, and in connection with that tribe Moses said nothing about priests.
Heb 7:15 This becomes even more evident when another priest arises in the likeness of Melchizedek,
Heb 7:16 who has become a priest, not on the basis of a legal requirement concerning bodily descent, but by the power of an indestructible life.
Heb 7:17 For it is witnessed of him, "You are a priest forever, after the order of Melchizedek."
Heb 7:18 For on the one hand, a former commandment is set aside because of its weakness and uselessness
Heb 7:19 (for the law made nothing perfect); but on the other hand, a better hope is introduced, through which we draw near to God.
Heb 7:20 And it was not without an oath. For those who formerly became priests were made such without an oath,
Heb 7:21 but this one was made a priest with an oath by the one who said to him: "The Lord has sworn and will not change his mind, 'You are a priest forever.'"
Heb 7:22 This makes Jesus the guarantor of a better covenant.
Rom 8:32 He who did not spare his own Son but gave him up for us all, how will he not also with him graciously give us all things?
Rom 8:33 Who shall bring any charge against God's elect? It is God who justifies.
Rom 8:34 Who is to condemn? Christ Jesus is the one who died—more than that, who was raised—who is at the right hand of God, who indeed is interceding for us.