Our Lord told His disciples that after His crucifixion, He will be with the Father in heaven. So the Roman soldiers actually helped God to fulfill His plan by sacrificing Jesus' physical body to redeem mankind. Our Lord having completed His work on earth is now in heaven preparing a place for each of us. This was to comfort His disciples that He was in full control of the situation.
John 14:4-5 "And where I go you know, and the way you know.” Thomas said to Him, “Lord, we do not know where You are going, and how can we know the way?”
What great surprises to our Lord to see that Thomas and possibly His other disciples were still ignorant of the gospel, that believing in Jesus Christ as the Son of God will give them eternal life in heaven. These disciples were with our Lord all these 3 years or so, and they still did not know their salvation. A real emergency had risen for our Lord would be betrayed that very night, and so how could these unlearned, naive and ignorant (possibly stupid to us) simple folks be expected to carry His gospel to the end of the world. Besides, their disappointment of His death, His failure to come as the King of the Jews and the fear of persecutions and martyrdom had blinded them.
John 20:21-22 So Jesus said to them again, “Peace to you! As the Father has sent Me, I also send you.” And when He had said this, He breathed on them, and said to them, “Receive the Holy Spirit."
Can you see what types of simple and ordinary people became His disciples then, but after the coming and empowering of the Holy Spirit (Book of Acts), these same disciples were immediately transformed into knowledgeable, wise, bold and powerful preachers of His everlasting gospel in truth.
Brethren, we too can be mightily used by Him if we express our faith in Him by obeying and keeping His words and commandments.