Chapter 1: The Senate's Impeachment Role :
Impeachment is a very serious affair. This power of Congress is the ultimate weapon against officials of the federal government, and is a fundamental component of the constitutional system of “checks and balances.” In impeachment proceedings, the House of Representatives charges an official by approving, by majority vote, articles of impeachment. A committee of representatives, called “managers,” acts as prosecutors before the Senate. The Senate Chamber serves as the courtroom. The Senate becomes jury and judge, except in the case of presidential impeachment trials when the chief justice of the United States presides. The Constitution requires a two-thirds vote of the Senate to convict, and the penalty for an impeached official is removal from office. In some cases, disqualification from holding future offices is also imposed. There is no appeal.
[Emphasis added to highlight the roles.]
Essentially, the Chief Justice becomes a trial court judge and will do all those things a trial court judge would do and with power subject to rules of the Senate. The rules appear quite similar to a common trial and are covered, below, in the RULES OF PROCEDURE ....
The following RULES OF PROCEDURE ... refer to the Presiding Officer of the Senate. The following clarifies who that person is during the impeachment trial.
Presiding Officer of the United States Senate:
When the Senate hears an impeachment trial of the President of the United States, by the procedure established in the Constitution, the Chief Justice is designated as the presiding officer.
RULES OF PROCEDURE AND PRACTICE IN THE SENATE WHEN SITTING ON IMPEACHMENT TRIALS:
Under some circumstances the Senate may overrule the Presiding officer.
Power of the Chief Justice during impeachment trial and defense.
Conclusion of the trial, final vote:
As stated above: There is no appeal. Furthermore, the Presiding Officer of the Senate (in this case, the Chief Justice) cannot overrule the vote.