The Synoptics on
50 Behold, a man named Joseph,
who was a member of the council, a good and righteous man
51 (he had not consented to their counsel and deed),
from Arimathaea, a city of the Jews,
who was also waiting for the Kingdom of God:
52 Going to Pilate, he asked for Jesus’ body.
53 Then he took it down, wrapped it in linen cloth and placed it in a tomb cut in the rock, one in which no one had yet been laid.
54 It was Preparation Day, and the Sabbath was about to begin.
55 The women who had come with Jesus from Galilee followed Joseph and saw the tomb and how his body was laid in it.
56 Then they went home and prepared spices and perfumes. But they rested on the Sabbath in obedience to the commandment.
Matt 27:57 When evening had come, a rich man from Arimathaea,
According to John 19:38-40, "Joseph of Arimathea asked Pilate for the body of Jesus. Now Joseph was a disciple of Jesus, but secretly because he feared the Jews. With Pilate’s permission, he came and took the body away. He was accompanied by Nicodemus, the man who earlier had visited Jesus at night. Nicodemus brought a mixture of myrrh and aloes, about seventy-five pounds. Taking Jesus’ body, the two of them wrapped it, with the spices, in strips of linen. This was in accordance with Jewish burial customs." However, the women wanted to add their own spices. But by the time they got around to it, Jesus had already risen. Jesus was buried the day before the Sabbath just before 6:00pm Friday. (The Jewish day actually starts at 6:00 pm) He rose early Sunday morning. If you're going to serve Christ, be prepared and get to it!
His enemies were concerned that the disciples would steal the body and falsely claim a resurrection occurred, and so had a guard posted at the tomb. By Jesus' enemies taking such steps, they inadvertently helped to validate the gospel claim of Jesus' resurrection. The disciple's couldn't have stolen the body because the guards were there. And the guards were eyewitnesses. consequently Jesus' enemies had a hard time trying to invalidate the resurrection.
Furthermore, the religous leaders had their own temple guards which they had command of. Why did they not simply use them to guard the tomb? Going to Pilate meant that they were requesting a Roman guard. I think most likely is because they didn't know who they could trust to guard the tomb. After all Joseph was a believer and yet on the Council. Who is to say if the temple guards would be reliable or sympathizers with the Jesus crowd! As outsiders the Romans would be the most reliable for the task. And no one would dare resist them. The word for "guard" in Matt 27:66 means, "A Roman guard which was made up of four to sixteen soldiers. In combat, they would form a square, and were able to hold off a much larger force." It is assumed that the seal was an official Roman seal made of wax which they used to seal. Not that the rock couldn't be move, but that illegally moving the rock would break the seal and incur a death penalty.
As for the timing of Jesus' death, in may be the case that God worked out the timing for Jesus to die and be buried just before the Sabbath to symbolize that the Christian, having died and been buried with Christ also enters into a Sabbath rest just as Jesus did. (Heb 4:9-11)