Paul's argument in chapter 5 compares Adam to Christ. The form of the argument suggests that all people are referred to here. While Paul says "many," he uses this for both Adam and Jesus.
But the free gift is not like the trespass. For if many died through one man's trespass, much more have the grace of God and the free gift by the grace of that one man Jesus Christ abounded for many. And the free gift is not like the result of that one man's sin. For the judgment following one trespass brought condemnation, but the free gift following many trespasses brought justification. For if, because of one man's trespass, death reigned through that one man, much more will those who receive the abundance of grace and the free gift of righteousness reign in life through the one man Jesus Christ.We know that Adam's sin affected all men. "Many" is talking about everyone in this passage; for both Adam and Jesus. Thus Jesus' death can justify all men, which disputes limited atonement. Lest any think that this justifies universalism, Scripture makes clear that some reject Christ. The passage is talking about what Adam resulted for men, and what Jesus accomplished for men; not what sins men would choose to do, nor whether men accept Christ's work. The gift is universal for those who want it. "Come, buy and eat! Come, buy wine and milk without money and without price." (Isaiah 55:1).
Therefore, as one trespass led to condemnation for all men, so one act of righteousness leads to justification and life for all men. For as by the one man's disobedience the many were made sinners, so by the one man's obedience the many will be made righteous. (Romans 5:15-19)
The next chapter rebukes the idea that men can sin in order that God's grace may be manifest, as Paul has also previously condemned in chapter 3. He implores us not to sin,
Let not sin therefore reign in your mortal body, to make you obey its passions.(Romans 6:12)Sinning is obedience to sin which is slavery to sin. And continuing in this path will pay the wages of death, but slavery to God will result in the gift of eternal life. Paul is talking to believers here, they are baptised with Christ in his death. Such unity in his death will certainly mean unity in his resurrection—if indeed you continue in the faith (Colossians 1:23). Paul refers to their status as slaves of sin before salvation (verse 20), but the warning against sin and encouragement in their ability to choose righteousness now they are in Christ implies that choice to sin is possible, and slavery to sin and hence the wages of sin is possible. This disputes perseverance/ preservation (as Calvinism defines it).
Chapter 9 is favoured as teaching unconditional election. I grasp this reading, though it fits more with Pharaoh as an individual, Esau and Jacob should probably be read collectively as this and the following chapters are talking about the nation of Israel (Jacob). It is not my intention to dwell on this chapter here, though I note that Peter (2 Peter 3:15-16) states that Paul can be hard to understand. If this is the case then it may be that passages like Romans 9 are difficult, and need to be understood in light of other passages. If we say the Calvinist reading of Romans 9 is clear this means significant amounts of Paul elsewhere is hard to understand, as well as several other authors of the Bible.
Nevertheless, in chapter 11 it is clear that what keeps us in the tree (kingdom of God) is faith. We are grafted in because of faith, and removed because of unbelief.
They were broken off because of their unbelief, but you stand fast through faith. So do not become proud, but fear. For if God did not spare the natural branches, neither will he spare you. Note then the kindness and the severity of God: severity toward those who have fallen, but God's kindness to you, provided you continue in his kindness. Otherwise you too will be cut off. And even they, if they do not continue in their unbelief, will be grafted in, for God has the power to graft them in again. (Romans 11:20-23).Both Arminians and Calvinists can agree here that salvation is connected to faith. I think this agreement should be remembered in discussions, and this fact receive significant emphasis. The disagreement is over the source of the faith: Is it God who provides the faith, or the person who responds to God in faith. Chapters 9 thru 11 are somewhat difficult in places; yet it seems to me that the association between disobedience and not understanding in chapter 10, and the exhortation to continue in God's kindness in chapter 11, would make most sense when faith is understood as a response to God.