The Roman soldiers sealed the tomb.
Then, they stood guard for the next three days in four hour shifts of four soldiers each.
How many Roman soldiers were there we do not know but could be as many as 50 or more and also a number of soldiers from the temple guard eg Jewish soldiers that worked at the Temple.
The stone that closed the entrance was very big and was rolled in a channel. This channel was slopped so it was easy to close but hard to open.
The Guards at the Tomb
62 The next day, the one after Preparation Day, the chief priests and the Pharisees went to Pilate. 63 "Sir,"they said, "we remember that while he was still alive that deceiver said, 'After three days I will rise again.' 64 So give the order for the tomb to be made secure until the third day. Otherwise, his disciples may come and steal the body and tell the people that he has been raised from the dead. This last deception will be worse than the first."
65 "Take a guard," Pilate answered. "Go, make
the tomb as secure as you know how." 66 So they
went and made the tomb secure by putting a seal on the stone and posting
These were regular Roman soldiers. A watch consisted of 4 soldiers which was changed every four hours. They would die if their prisoner escaped.
These soldiers were not from the temple guard. Like the group that came to imprison Jesus.