The Romans were trying to keep a people under subjugation by force. It was Roman word that Jesus be crucified, it was a Roman seal on the tomb and it was Roman guards keeping watch. A missing body sends a terrible message to the masses under the thumb of this ruler.
The inability of the roman authority to produce the body of Jesus was powerful testimony to the authenticity of the resurrection accounts. If the most powerful army and governing force on earth couldn’t produce a body, who could?
The Roman government would have benefitted from producing Jesus’ corpse. They would have been trying to protect Rome from an uprising. The fact that they couldn’t produce a body adds more proof to the resurrection. It helps to establish the resurrection as fact.
To stop a rebellion against Rome. Rome was powerful they would have had enough resources to have been able to find his body. Rome not being able to produce a body is significant.