What is your definition of the Church? When someone asks, "what is the church's role in…" what entity are they asking about?
What it is not
The Church, is not the building, of course. No one disagrees with that. But, neither is it a structure, such as the Presbyterian Church of Canada, or the Anglican Church. Their position is that the church is represented by an Archbishop, or President in Council, whether at a Synod, or Session.
What it is
But the Church in Scripture is defined organically. It is "the body of Christ" (Col 1:24), of which we are "members" (Eph. 5:30). It is the group over which he has been given, all authority, as "head" over her (Col 1:18 cf. Eph. 5:24). Generally speaking then, "the Church", can be referred to as that universal body of Christ, composed of all people everywhere, who are engrafted by the Spirit, into Him. Acts 9:21 implies this as it speaks of the "church throughout all Judea, Galilee and Samaria".
The very word, church, is a translation of the Greek word for "assembly" (ekklesia). Thus, in a very real sense, the church is the body of Christ "assembled". So we read of Paul and his companions, that they "appointed elders for them in every church" (Acts 14:23), and "He met with the Church" in Antioch (11:26), but later in 15:4, "When they arrived at Jerusalem, they were received by the church". Thus in each place, Luke can speak of "the Church". The Epistles of the New Testament are written to specific churches, Paul writing, "to athe church of God which is at bCorinth" (I Cor. 1:2). This is the most common use of the word "church" in Scripture and the ordinary way in which one ought to think of "the Church."
Congregationalism
Recognizing this, Baptists, have been from the earliest days, Congregationalists. In 1644, seven Baptist Churches in London gathered together and wrote a confession, including the following teaching on the church. This:
Church is a company of visible saints, called and separated from the world by
the word and Spirit of God, to the visible profession of faith of the gospel,
being baptized into that faith, and joined to the Lord, and each other, by
mutual agreement in the practical enjoyment of the ordinances commanded by
Christ their head and king. (Article XXXIII)
And of this visible, local assembly, they professed:
BEING thus joined, every church hath power given them from Christ, for their
wellbeing, to choose among themselves meet persons for elders and deacons, being
qualified according to the word, as those which Christ hath appointed in His
testament, for the feeding, governing, serving, and building up of His Church;
and that none have any power to impose either these or any other (Article
XXXVI).
Under this biblical distinctive the congregation itself is finally accountable to God for endorsing leadership, doctrinal fidelity, gospel witness, and stewardship. This has a great effect on our view of "doing church". It is not a building program, or an activity, but an assembly of the living body of Christ, to do His will.