A manorial roll is a fancy name for a list of all the people who worked on a big piece of land called a manor. Imagine there's a huge field with a big house in the middle. The person who owns the field is called the lord of the manor. He has many people working for him who live on his land. These people are called peasants.
The manorial roll is like a big list that the lord of the manor writes down every year. He writes down the names of all the peasants who work on his land. This list is important because it helps the lord of the manor keep track of who is working for him and how much they owe him.
Sometimes, the lord of the manor would give the peasants a little piece of land to farm on their own. The manorial roll would also list the names of these peasants and the small piece of land they were given.
So, the manorial roll is basically a list that the lord of the manor uses to keep track of all the people who work for him on his big piece of land.