According to The Phrase Finder:

It is “roll” as in list of names (from Merriam-Webster online):

Main Entry: roll
Pronunciation: \’rOl\
Function: noun

Etymology: Middle English rolle, from Old French, from Latin rotulus, diminutive of rota wheel; akin to Old High German rad wheel, Welsh rhod, Sanskrit ratha wagon
Date: 13th century

1 a (1) : a written document that may be rolled up : SCROLL; specifically : a document containing an official or formal record. The rolls of parliament. (2) : a manuscript book b : a list of names or related items : CATALOG c : an official list: as (1) : MUSTER ROLL (2) : a list of members of a school or class or of members of a legislative body