Can an unmarried Roman Catholic who has received absolution for the sin of having a vasectomy ever become married in the Catholic Church?
Sterility is not an impediment to marriage. It is the permanent inability to consummate a marriage by either the man or the woman that is an impediment. So, yes, such a man can be married in the Church, but he should reveal his sterilization to his fiancee and to the priest or deacon who is preparing him and his fiancee for marriage. If either he or the fiancee see marriage to each other as a means to be married without being open to life, then that could impede sacramental consent and invalidate the marriage.