What is Reverend Parris's role throughout Act 3 of The Crucible?
In Act Three, Reverend Parris plays the role of antagonist, judge, and accuser. He again reveals that he is a selfish, wicked man whose only intentions are protecting his reputation and position throughout the community by siding with the court. When Proctor approaches Deputy Governor Danforth with a signed deposition from Mary Warren stating that the girls are frauds, Parris tells Danforth not to trust Proctor because he is a mischief. Parris insists that Proctor's goal is to overthrow the court and tries his best to influence Danforth to dismiss Proctor and Mary's claims. Parris also accuses Proctor of not attending church on a regular basis and even compares him to Cain. When Proctor presents signatures of land-owning citizens of Salem that believe the accused members are innocent, Parris suggests that each person should be summoned to the court for questioning. Parris is clearly the antagonist throughout the scene and accuses Proctor of attempting to overthrow the court. He also cast judgment on those who believe that innocent people are being tried unfairly.
I have edited your question because you asked two. You are only allowed one question per entry.
In Act III, I really start to get mad at Rev. Parris. Everything he says is accusatory, and the only thing he ever has to back any of it up is that John Proctor doesn't go to church regularly. So, this must make him a sinner.
Parris puts himself in the role of a self-appointed judgement. He does this with an accusing tone and he presumes it is his right to ask questions just like the magistrates. When Proctor presents information, if it feels like the magistrates might be swayed by it, Parris will smurk or smile as if to presume that they couldn't possibly believe such untruth... since it is a sinner telling it.
Parris almost tries to act like a DA or prosecuting attorney, although these cases didn't really include any attorneys. He has become a sarcastic person who has one goal in all of this: covering his own self and making sure he doesn't go down because witchcraft was in his house.