A nationwide consultation on opening the Roman Catholicpriesthood to women has drawn criticism from the hierarchy of the church even before it begins at noon today in Baltimore.

Archbishop John R. Quinn of San Francisco, president of the National Conference of Catholic Bishops, told conference organizers that the theme of their conference is not "legitimate." He counseled that they should limit their deliberations to more general considerations of the role of women in the church exclusive of the priesthood.

The Vatican, Quinn said, "has clearly taught that fidelity to the apostolic tradition makes it impossible for the Catholic Church to ordain women to the priesthood."

For that reason, he continued, "I would not take part in or give encouuragement to" the conference. The weekend conference was organized by an ad hoc group of lay women, nuns and some priests. It has the backing and 40 Catholic organizations, including the major national organizations of both priests and nuns.

The meeting is the second such unofficial national gathering focusing on ordination of women in the Roman Catholic Church. An earlier session, held in Detroit three years ago, is generally considered to be a factor in moving the late Pope Paul VI to issue a formal proclamation in 1977 reaffirming the church's traditional exclusion of women from the priesthood.

Quinn's letter, which was made public by the hierarchy's press office, was in response to an invitation to him from Sister Mary Luke Tobin, one of the conference organizers, to attend the gathering.

He told Tobin that the group could make "an important contribution . . . if instead of taking up the question of ordination of women, you could pursue the question of the role of women in accord with the doctrinal position of the church, if you could search out and identify ways in which present roles can be reinforced and new roles can be developed for building up the body of Christ in unity of faith and charity."

He added that "the desire of women for an expanded role in the church is one we sincerely want to respond to, and it is an area in which we bishops really need and want help."