How many Roman soldiers came to arrest Christ? Answer – None – the guard force was from the Temple guard. A Roman guard would not have taken Jesus to the High Priest’s house but to the Roman fortress to be held.
"The band of soldiers (tên speiran). No word for "of soldiers" in the Greek, but the Latin spira (roll or ball) was used for a military cohort (Polybius 11, 23, 1) as in Matthew 27:27; Acts 10:1, etc., here for a small band secured from the Tower of Antonia" (Robertson's Word Pictures in the New Testament).
"The "cohort" in the regular Romans legions typically had 600 men but could number as many as 1,000 in the auxiliary forces (all New Testament references, apparently; see Bruce, New International Commentary on the New Testament, Acts, p. 202)." [The Complete Biblical Library Greek-English Dictionary].
"Then the detachment of troops and the captain and the officers of the Jews arrested Jesus and bound Him" (John 18:12). Notice that though a captain is an officer, he is listed separately from the Jewish officers. Thus, the soldiers arresting Jesus were under a non-Jewish captain -- in other words, this was a Roman band. In every case, the use of speiran in the New Testament refers to a Roman band of soldiers (Matthew 27:27; Mark 15:16; John 18:3, 12; Acts 10:1; 21:31; 27:1) and the use in John 18 is particularly clear that it was a Roman band.
It is possible for the Roman government to loan out soldiers. Pilate loaned the Jews a group to secure the tomb. "Pilate said to them, "You have a guard; go your way, make it as secure as you know how"" (Matthew 27:65), which explains why they reported the resurrection to the Jewish priests first before going to Pilate. "Now while they were going, behold, some of the guard came into the city and reported to the chief priests all the things that had happened" (Matthew 28:11).