Rostering is like making a list of people who will do tasks at a certain time. It's like when you and your friends decide who will go first when playing a game. "Roster" means a list of names or a group of people who work together.
For example, imagine you're having a sleepover with your friends, and you want to make sure everyone gets a turn choosing what game to play. Your mom could help by making a roster or a list of who will pick the game and in what order. This way, everyone will know when it's their turn to choose and no one will feel left out.
Similarly, in a workplace or a sports team, rostering means deciding who will work or play at certain times. Your boss or coach will make a roster or a plan for who will be working or playing when, so everyone knows their schedule and can plan accordingly.
In short, rostering means making a plan or a list of people who will do tasks or activities at a certain time.