What is an electoral roll? why is it really important?

Voter registration was an achievement of the Progressive Movement in the late 1800s/early 1900s. Before voter registration, all one had to do was to swear that they lived in the precinct before an election officer. This led to corruption, as political bosses would control the precincts and have people vote at multiple ones to get their candidate in power. As voter registration requires that all voters register and are igned a precinct, electoral rolls confirms your registration.