How many years in prison did roland gary service for killing a religious leader?

20 years.

Explanation:

Roland Gary killed a religious leader Robert Hardcastle nearly twenty years ago, stabbed him to death, he was found guilty of his crimes and then sentenced to death row, a fate which finally reached him 20 years later in a prison in Oklahoma. He always claimed that the stabbing of Mr. Hardcastle was done in self-defense, but neither the court or the appellation trials believed him enough to save him from the death penalty, he served 20 years in prison before being executed with lethal injection.

britian is way too advanced for me my good luck