Romans 7 - Power of the Gospel and the Law 2

In one of the most misused and misunderstood books Paul declares that Christians are free from the Law but yet the Law served its purpose by making sin obvious. The Law of Moses did not provide justification. People of faith under that system were reminded every year of their sin in the offering of animals. But the atoning death of Jesus and the power of the Gospel can declare one righteous..but how and when?