In 1976 the Roman Ritual was revised and split into two books: The Rites and The Book of Blessings (which has been greatly revised). The Book of Blessings now has the marriage blessing. 1987 Index:
USCCB 1-55586-346-9, Book of Blessings (Liturgy Documentary Series 9) (5/18/2004) seems to be out of print now.
But another version, I believe, is from 1989 (ISBN-10: 0814618758, Liturgical Press):
Book of Blessings: Approved for Use in the Dioceses of the United States of America by the National Conference of Catholic Bishops and Confirmed by the Apostolic See (Roman Ritual)
Older Roman Ritual (from 1964), Celebration of a Silver or Golden Wedding Anniversary.