“There's a seating chart in the back of the roll book.”
You're a teacher. You had to take a day off of work because of a family issue. You're writing a note for the substitute teacher, explaining what to do. One of your instructions is about where the students should sit:
There's a seating chart in the back of the roll book.
A "seating chart" is a chart or drawing which shows where certain people are supposed to sit.
Seating charts are used:
at very formal meetings, like at the United Nations
When something is printed in the last few pages of a book, you can describe it as "in the back":
There's an index in the back of the book. Try looking there.
The answers are printed in the back of the book.
A "roll book" is a book that a teacher uses to keep track of which students attended each class. The teacher marks who's missing each day in his or her "roll book".
The word "roll" means an attendance list. You may also hear the phrase "take the roll":
Guys, let me take the roll and then we'll get started.