Sorry, I should have clarified. The discourse marker in Romans 5:1 is "been" = Having been justified. But I could also argue that the marker is in 4:25, when Paul says "and"
It's really a transition of thought that takes place over the course of about 10 verses. I will say that my understanding of this transition (and the next 7 chapters) steps on a lot of doctrinal toes.
Paul had just demonstrated in the first 4 chapters that man has rejected God, so God gave them over; that every man is without excuse; that being a Jew is of no benefit; all have sinned; that an imputed righteousness is necessary; that this righteousness comes through faith, without works; Abraham as the example of one who "believed in God" and was credited as righteous. And that this is to everyone one believes in Him who raised Jesus from the dead (4:24).
Now here is the beginning of the transition:
He who was delivered over because of our transgressions, and was raised because of our justification (4:25).
The transition is complete in 5:9-10:
Having been justified by His blood, we shall be saved from the wrath of God through Him....having been reconciled, we shall be saved by His life.
Paul makes a transition from why Jesus died, to why He was raised. But this issue of why He was raised brings with it many associated lines of thought.
Jesus died to pay the penalty for our sin. He was bruised for our transgressions, and crushed our our iniquities. This speaks nothing of why He was raised. As proof that God had accepted the sacrifice? Yes, but that's not the end of it.
Paul makes a transition from Jesus' death for our sins, to His resurrection as the first fruits of resurrection (1Cor 15:20). Compare the wording in Romans 5:12-21 to 1Corinthians 15:20-23, 52-54, Both Romans 5 and 1Cor 15 speak of the universality of physical death (for everyone) because of Adam, and physical resurrection for everyone because of Christ - compare to John 5:28-29. Everyone will be raised physically. That's why the lake of fire will not consume the wicked, they will have a physical body that is immune to death.
Then, as Paul made a brief mention in 1Cor 15:23 & 52, our resurrection will happen when Christ returns in glory. We must be resurrected in order to inherit the Kingdom of God with Christ. Paul said as much in 1Cor 15:50 - flesh and blood cannot inherit the Kingdom of God. Compare to Matthew 19:28-29: "In the regeneration (physical resurrection), when the Son Of Man will sit on His glorious throne..."
These are so intertwined that one cannot happen without the other. He returns as the King of Glory, and we are raised imperishable at that time. He rewards His faithful, who become joint-heirs with Him (Rom 8:17).
This is the entire thrust of Predestination in chapters 8-9. It has absolutely nothing to do with who believes the gospel, or who is born again, or anyone being chosen to be saved from hell.
It has everything to do with those who God foreknew as sons, or joint-heirs with Christ. Mark 10:35-40 gives a good picture of this:
35 James and John, the two sons of Zebedee, *came up to Jesus, saying, “Teacher, we want You to do for us whatever we ask of You.”
36 And He said to them, “What do you want Me to do for you?”
37 They said to Him, “Grant that we may sit, one on Your right and one on Your left, in Your glory.”
38 But Jesus said to them, “You do not know what you are asking. Are you able to drink the cup that I drink, or to be baptized with the baptism with which I am baptized?”
39 They said to Him, “We are able.” And Jesus said to them, “The cup that I drink you shall drink; and you shall be baptized with the baptism with which I am baptized.
40 But to sit on My right or on My left, this is not Mine to give; but it is for those for whom it has been prepared.”
Compare this with Hebrews 2:9-11:
9 But we do see Him who was made for a little while lower than the angels, namely, Jesus, because of the suffering of death crowned with glory and honor, so that by the grace of God He might taste death for everyone.
10 For it was fitting for Him, for whom are all things, and through whom are all things, in bringing many sons to glory, to perfect the author of their salvation through sufferings.
11 For both He who sanctifies and those who are sanctified are all from one Father; for which reason He is not ashamed to call them brethren
Jesus was crowned with glory and honor because He suffered. Those who pick up their cross will become joint-heirs with Him, and share in His glory. This happens "in the regeneration"
The writer of Hebrews calls it "inheriting salvation" (1:14).
Paul said in Colossians 3:23-24:
Whatever you do, do your work heartily, as for the Lord rather than for men, knowing that from the Lord you will receive the reward of the inheritance. It is the Lord Christ whom you serve.
God foreknew those who would persevere in faith, and become joint-heirs with Christ. Not that He foreknew what hey would do (although that is the case too), but that He foreknew "them" as sons. And those He foreknew, He placed on the road to suffering with Christ, because that is the criteria by which on will be found faithful.
In chapter 8, right after Paul speaks of becoming joint-heirs with Christ "IF" we suffer with Him, he goes into predestination. then right in the midst of predestination, he speaks of suffering:
35 Who will separate us from the love of Christ? Will tribulation, or distress, or persecution, or famine, or nakedness, or peril, or sword?
36 Just as it is written, “For Your sake we are being put to death all day long;
We were considered as sheep to be slaughtered.”
37 But in all these things we overwhelmingly conquer through Him who loved us.
38 For I am convinced that neither death, nor life, nor angels, nor principalities, nor things present, nor things to come, nor powers,
39 nor height, nor depth, nor any other created thing, will be able to separate us from the love of God, which is in Christ Jesus our Lord.
Chapter 9 is about how it is by God's choice that some will receive glory and others won't. It's because HE placed them on a path to be conformed to the image of Christ, not because of anything inherently good in the man. He uses Israel as the example. God did not choose Israel because they were great, but because of His faithfulness (Deut. 7:7-8).
Paul's hope for Israel is that they would also receive the eternal inheritance. NOT that they would be allowed to be saved from hell, or go to heaven. But the inheritance. It is to those who confess Jesus Christ as Lord (10:9-10), who are known by His Name (10:13).
Paul does not have conversion in mind, but one who confesses Christ in times of suffering. Compare to Matthew 10:22-33. He who is known by the Name of the Lord, and confesses Him during times of persecution, and endures to the end, will become a joint-heir with Christ "in the regeneration", when Christ returns
Paul is absolutely NOT advocating a superstitious "sinner's prayer"
It is when Jesus returns that "all Israel will be saved". Not converted, but heirs of the eternal inheritance, because they will suffer in the Tribulation
The gist of all this is that Paul dealt with the spiritual aspect of sin and redemption in chapters 1-4, then moves into the physical resurrection (and things associated with it) in chapters 5-11
