A more thorough explanation:

The Keeper of the Rolls, also known as Custos Rotulorum, is a legal term that refers to the principal justice of the peace in a county. This person is responsible for keeping the rolls of the county sessions of the peace.

For example, if someone is arrested in a county, the Keeper of the Rolls would be responsible for keeping track of their case and any legal proceedings that follow. They would also be responsible for maintaining records of any other legal matters that take place in the county.

The role of Keeper of the Rolls dates back to medieval times, when written records were kept on rolls of parchment. Today, the role still exists in some countries, although the responsibilities may have changed over time.