Called by his Spirit to become Christians.  He called, not merely by an external invitation, but in such a way as that they in fact were justified.  This cannot refer simply to an external call of the gospel, since those who are here said to be called are said also to be justified and glorified.  The meaning is, that there is a certain connection between the predestination and the call, which will be manifested in due time.  The connection is so certain that the one infallibly secures the other. (Dr. Albert Barnes)

That he might now by a clearer proof show how true it is that a conformity with the humiliating state of Christ is for our good, he adopts a graduating process, by which he teaches us, that a participation of the cross is so connected with our vocation, justification, and, in short, with our future glory, that they can by no means be separated. (John Calvin)

The Gentiles, whom He determined to call into his Church with the Jewish people, He called - He invited by the preaching of the Gospel, to believe on his Son Jesus Christ.  It is worthy of note, that all that is spoken here refers to what had already taken place; for the calling, justifying, and glorifying are here represented as having already taken place, as well as the foreknowing and the predestinating.  It is therefore reasonable to suppose that the apostle refers to what God had already done among the Jews and Gentiles: though he may also speak of the things that were not as though they were. (Dr. Adam Clarke)

them he also called; not to afflictions: many may be called to afflictions, and endure them, who are neither justified nor glorified; besides, the people of God, though they meet with many afflictions, between their call to eternal glory, and their enjoyment of it, yet they are not so much called to afflictions, as to patience under them: their call is of grace, by special grace, to peculiar blessings of grace, and to a kingdom and glory; and this their calling is secured by predestination, and connected with glorification: and whom he called (Dr. John Gill)

Whom he did predestinate those he also called, not only with the external call (so many are called that were not chosen, Matthew 20:16; Matthew 22:14), but with the internal and effectual call.  The former comes to the ear only, but this to the heart.  All that God did from eternity predestinate to grace and glory he does, in the fullness of time, effectually call. The call is then effectual when we come at the call; and we then come at the call when the Spirit draws us, convinces the conscience of guilt and wrath, enlightens the understanding, bows the will, persuades and enables us to embrace Christ in the promises, makes us willing in the day of his power.  It is an effectual call from self and earth to God, and Christ, and heaven, as our end - from sin and vanity to grace, and holiness, and seriousness as our way.  This is the gospel call.  Them he called, that the purpose of God, according to election, might stand: we are called to that to which we were chosen. So that the only way to make our election sure is to make sure our calling, 2Peter 1:10. (Matthew Henry)

The word “called” (as Hodge and others truly observe) is never in the Epistles of the New Testament applied to those who have only the outward invitation of the Gospel (as in Matthew 20:16; Matthew 22:14).  It always means “internally, effectually, savingly called.” It denotes the first great step in personal salvation and answers to “conversion.”  Only the word conversion expresses the change of character which then takes place, whereas this “calling” expresses the divine authorship of the change, and the sovereign power by which we are summoned, Matthew-like, Zacchaeus-like, out of our old, wretched, perishing condition, into a new, safe, blessed life. (A Commentary on the Old and New Testaments by Robert Jamieson, A. R. Fausset and David Brown)

The called. These have been called by the gospel and have accepted the call.  Many others are called, Jews and Gentiles, but only those who hear and obey are chosen (Matthew 20:16; Matthew 20:14).  Paul uses the term of the latter class; those who hear and obey.  The evidence that we are "the called" is that we love God. (The People's New Testament (1891) by B. W. Johnson)

Rom 8:30 Them he - In due time. Called - By his gospel and his Spirit.  And whom he called - When obedient to the heavenly calling, Acts 26:19.  He also justified - Forgave and accepted.  And whom he justified - Provided they "continued in his goodness," Romans 11:22, he in the end glorified - St. Paul does not affirm, either here or in any other part of his writings. that precisely the same number of men are called, justified, and glorified.  He does not deny that a believer may fall away and be cut off between his special calling and his glorification, Romans 11:22.  Neither does he deny that many are called who never are justified. He only affirms that this is the method whereby God leads us step by step toward heaven.  He glorified - He speaks as one looking back from the goal, upon the race of faith. Indeed grace, as it is glory begun, is both an earnest and a foretaste of eternal glory. (John Wesley)