According to the General Instruction of the Roman Missal, the priest is to take the Book of the Gospels to the ambo and then proclaim the Gospel. While it’s implied that the priest read from the text, there’s no written requirement. However, he is required to have the text in front of him when he recites the Gospel.
If the Book of the Gospels is on the altar, the priest then takes it and goes to the ambo, carrying the Book of the Gospels slightly elevated and preceded by the lay ministers, who may carry the thurible and the candles. Those present turn towards the ambo as a sign of special reverence to the Gospel of Christ. . . . The priest incenses the book, if incense is used. . . Then he proclaims the Gospel and at the end says the acclamation Verbum Domini (The gospel of the Lord), to which all respond, Laus tibi, Christe (Praise to you, Lord Jesus Christ). The priest kisses the book, saying quietly, Per evangelica dicta (May the words of the Gospel). (GIRM 133-134)