Short answer: The most likely author of Romans 8:28 is the Apostle Paul. Evangelical Christians affirm Paul as the inspired, apostolic author of the Epistle to the Romans and treat his teaching in Romans 8 (including 8:28) as authoritative Scripture.

Key points evangelicals typically emphasize about Paul and Romans 8:28

– Paul’s identity and credentials
– Paul (formerly Saul of Tarsus) was a Jewish Pharisee turned Christian apostle (see Acts 9; Philippians 3:4–7 for his background).
– He was trained under Gamaliel (Acts 22:3), a Roman citizen (Acts 22:25–29), and a leader in the early missions (Acts 13–28).
– He identifies himself as the author at the start of Romans (Romans 1:1, 1:7) and elsewhere in the New Testament writes many letters now in the New Testament canon.

– Historical and church testimony for Pauline authorship
– Romans has been attributed to Paul from the earliest days of the church. Early Christian writers and lists (e.g., Clement of Rome, Irenaeus, the Muratorian Fragment) accept Paul’s authorship.
– Within mainstream evangelical scholarship Romans is generally accepted as authentically Pauline without serious dispute.

– When and why Paul wrote Romans
– Paul likely wrote Romans in the mid-to-late 50s AD (commonly dated around AD 56–58), probably from Corinth shortly before his trip to Jerusalem.
– His purpose was to present a systematic statement of the gospel and to prepare for his hoped-for visit to Rome, addressing both Jewish and Gentile believers and themes of sin, justification, sanctification, and God’s purposes for the church.

– How Paul’s background shapes Romans 8:28
– Romans 8 is a central section of Paul’s theology of life in the Spirit, assurance, and God’s ultimate sovereignty and love for believers.
– Paul’s own experience of suffering, mission, and perseverance (he faced opposition, imprisonments, shipwrecks, etc.) informs his pastoral confidence that “God works all things together for good” for those who love Him (Rom. 8:28).
– The clause “those who are called according to his purpose” ties into Paul’s emphasis on God’s initiative in salvation (calling, justification, sanctification) while also calling believers to faithful love and obedience.

– Theological emphases relevant to evangelicals
– Inspiration and authority: Evangelicals hold Paul’s letters to be God-breathed Scripture (2 Timothy 3:16), so Romans 8:28 is treated as authoritative doctrine and pastoral comfort.
– Sovereignty and assurance: Paul teaches both God’s sovereign control over events and the believer’s secure position in Christ—assurance that trials serve God’s redemptive purposes.
– Sanctification and ultimate good: “Good” is understood not simply as comfort or temporal blessing but ultimately conformity to the image of Christ (Romans 8:29), the believer’s growth into God’s purposes.
– Pastoral application: Paul’s pastoral heart means Romans 8:28 is often used pastorally to encourage Christians facing suffering to trust God’s purposes, while maintaining biblical balance between God’s providence and human responsibility.

– Recommended evangelical resources on Paul and Romans
– Commentaries: Douglas Moo (NIVAC/BECNT), Thomas R. Schreiner (Baker Exegetical Commentary), John Stott’s shorter treatments of Romans.
– Biographical and theological studies: Works on Paul’s life (e.g., N. T. Wright’s Paul books, though some evangelicals differ with Wright’s conclusions), and classic evangelical expositions such as those by John Murray or John Piper on Romans.

If you want, I can:
– Summarize Paul’s life in a brief timeline,
– Give a short exegesis of Romans 8:28 in its immediate context,
– Or list specific evangelical commentaries or sermons that treat Romans 8:28.