Final answer:
The roles of the U.S. Senate, particularly related to presidential appointments and treaties, are to provide advice and consent for nominations made by the President and to ratify treaties negotiated by the President. The Senate plays a crucial role in the appointment process and the approval of international agreements.
Step-by-step explanation:
The U.S. Senate has important roles in relation to presidential appointments and treaties. Regarding presidential appointments, the Senate provides the 'advice and consent' to the President's nominations. This means that the President needs majority approval from the Senate to appoint officials in government, including judges and officers of the Executive Branch. In the case of treaties, the President has the power to negotiate them, but a two-thirds vote of the Senate is required to ratify the treaties.