Roll film is the name for a number of formats for photographic film. Roll film is wound on a spool, as opposed to sheet film which comes in cartridges. The most common formats of roll film are the format 120, and the format 220, which are both used in medium format cameras. Even though the common 35 mm film is also wound on a spool, it is not called roll film.
Images for kids
A spool of Fujifilm-brand type 120 negative rollfilm
Roll film Facts for Kids. Kiddle Encyclopedia.