Short answer: The most-likely author is the Apostle Paul. Evangelical Christians affirm Pauline authorship of Romans (including 10:9–10) and treat Paul as an authoritative apostle whose life and teaching shaped the gospel and doctrine of justification by faith.

Key facts about Paul (evangelical perspective)
– Identity and background: Paul (born Saul of Tarsus) was a Jew, trained as a Pharisee (Acts 22:3; Phil. 3:5), a Roman citizen (Acts 22:25–29), originally persecuted the church, and was dramatically converted after encountering the risen Jesus on the Damascus road (Acts 9).
– Apostolic role: Jesus commissioned Paul as an apostle to the Gentiles (Acts; Gal. 2:7–8). He planted many churches on missionary journeys and carried significant pastoral and theological authority in the early church.
– Authorship of Romans: Paul himself identifies as the author (Romans 1:1), and early church testimony (e.g., Clement of Rome, Irenaeus) and the internal style, theology, and historical context support Pauline authorship. Evangelicals date Romans to about AD 55–58 (commonly c. AD 57), written from Corinth during Paul’s third missionary journey, to the mixed Jewish-and-Gentile church in Rome.
– Role in the canon: Evangelicals view Paul’s epistles as inspired Scripture (2 Timothy 3:16) and authoritative for doctrine and practice.

Why Romans 10:9–10 matters to evangelicals
– The verses: Romans 10:9–10 (ESV paraphrase) — “If you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved. For with the heart one believes and is justified, and with the mouth one confesses and is saved.”
– Core theological points:
– Salvation by faith: These verses summarize Paul’s teaching that justification (being declared righteous before God) comes through personal faith in Christ (belief in the heart).
– Lordship of Christ: Confession that “Jesus is Lord” signals allegiance and submission to Christ’s authority—not merely intellectual assent.
– Resurrection central: Belief that God raised Jesus from the dead is the decisive event that grounds Christian hope and justification.
– Word-and-respond dynamic: Evangelicals emphasize that the gospel is to be believed inwardly and confessed outwardly; both inward faith and outward confession are part of the biblical witness to salvation.
– Evangelical practice and pastoral application:
– Romans 10:9–10 is often used in evangelism and discipleship as a succinct statement of the gospel and as an understandable way to explain how to receive salvation.
– Many evangelicals caution against reducing the passage to a mechanical “sinner’s prayer” formula. They stress that true saving faith is more than a single spoken sentence—it is trust in Christ that results in repentance, ongoing obedience, and life changed by the Spirit.
– The verses underpin evangelistic tools like the “Romans Road” because they link personal faith and public confession to the promise of salvation.

Further study (evangelical resources)
– Commentaries: John Stott’s The Message of Romans; Douglas Moo, The Epistle to the Romans (Pillar); D. A. Carson’s treatment in various collected works.
– Bible translations often recommended by evangelicals: ESV, NASB, NIV for clarity in Romans.

If you’d like, I can:
– Give a short exegesis of the Greek words used in 10:9–10 (homologeō, pisteuō, dikaioō) and how evangelicals understand them.
– Summarize how Romans 10 fits into the broader argument of Romans (justice, faith, Israel, mission).
– Provide a concise evangelistic wording based on 10:9–10 with pastoral cautions.