Each roll that you shoot becomes a camera roll. It is often helpful to label them with a number in the order that they were shot. The usual way is with the abbreviation C.R. followed by a number. The lab will then assemble and print them in that order. This makes things less confusing when you first get back your footage.
Glossary of Film Terms - http://homepage.newschool.edu/~schlemoj/film_courses/glossary_of_film_terms/
reprinted with permission