Why did Jesus accept baptism by John?

Jesus accepted baptism from John because "it is proper for us in this way to fulfill all righteousness.

What religious ritual is associated with John the Baptist?

The religious ritual associated with John the Baptist was baptism. This ritual means people accepted their sinfulness and desire for God's Kingdom.

What role did John the Baptist play in the ministry of Jesus?

John the Baptist played the role of preparing for Jesus' ministry by calling people to an awareness of their sins, and to repent.