We are given here a varied list of services of the saints: some teachers, others, of note among the apostles, kinsmen, and others. Phoebe, a servant of the Church, heads the list. Whether it be the Apostle Paul or Phoebe, each fills his or her place according to the grace given and will in a coming day be rewarded at the judgment seat of Christ, not for how much was done by each, but whether or not it comes from the heart and is carried out through grace given of God.
The matter of divisions, so prominent among God's people, was also before the apostle and he cautioned the saints to avoid heretics.
We are to be wise concerning good and simple concerning evil; how much good the heart has to rest upon the mercy of salvation, the Father's house, the body of Christ.
In the epistle to the Romans we are given to see the divine purpose for the Church, also Israel's blessing, each in a separate sphere. Although these blessings are found through and in the same Savior, unless they were brought into the Church at Pentecost, as the remnant of Jews were, the blessings of the Jew were and always will be earthly, the millennial kingdom and the new earth (Isa. 45:1818For thus saith the Lord that created the heavens; God himself that formed the earth and made it; he hath established it, he created it not in vain, he formed it to be inhabited: I am the Lord; and there is none else. (Isaiah 45:18)).
The "mystery" concerns Christ and the Church formed at Pentecost.
The prophetic Scriptures, the epistles, chiefly of Paul the apostle, give us the mystery and all the heavenly blessings that parallel and follow the millennium.