According to the Gospel accounts, they cast lots for the robe of Jesus. This was according to fulfill an Old Testament prophecy.
Very little is known about Roman crucifixion and this relies on scraps of information and just a few archaeological discoveries. For example, the Gospel accounts of guards at the crucifixion are supported by a anecdote in the fragmentary novel Satyricon of Petronius, the so-called grieving widow story.
Bent nails have been discovered (ostensibly associated with crucifixion sites) as well as the ankle bone of a crucifixion victim in Jerusalem. The captives from the Spartacus slave revolt were crucified along the Appian Way, as related by Roman historians.
As for literary evidence, there are the Gospel accounts of Jesus' s crucifixion, and the accounts of crucifixions during the Jewish revolt as related by a witness, Josephus.
The Roman soldiers at the crucifixion kept spectators back, perhaps ate lunch, and played games by scrawling playing boards on the ground (the lots for Jesus's robe were possibly incorporated into this). While crucifixion victims were normally kept on the cross after death, Pontius Pilate acceded to Jewish Sabbath and burial customs and permitted the body of Jesus to be taken down and placed in a tomb.
According to the Gospel of Matthew, Pilate ordered the tomb to be sealed and a guard to be placed over it, as the Jewish authorities were supposedly aware of the prediction Jesus would rise in three days.
Secular scholars insist the entire story was a fabrication, or large parts of it, and what you want to believe is a matter of Faith. But this is what the sources indicate. The Gospels provide a fairly detailed account of the scene and of the Roman soldiers at the crucifixion.