Role relates to people’s functions and to parts played by performers. Roll is broader, having many definitions, including (1) to move by repeatedly turning over, (2) to recur, (3) a register or catalogue, (4) a list of names, (5) a deep rumble, (6) a rapid succession of short sounds, and (7) a scrolled piece of parchment or paper. That fourth definition is the one meant in the phrase roll call, which is commonly misspelled role call.
The homophones roll and role actually have a common origin—the Latin rotula, diminutive of wheel—but they differentiated long ago and share no common ground in modern English.
Glenn Close has played many big roles in her career. [New York Daily News]
She has been on the honour roll throughout her years here. [Calgary Herald]
She’s a brilliant role model and style icon. [Daily Mail]
Liberia has made a bid for funding from the Gavi to roll out the pneumococcal vaccine against pneumonia next year. [Guardian]
British troops, NATO officials say, will also remain in Afghanistan long past the end of 2014, largely in training or mentoring roles. [Sydney Morning Herald]
Good thing they’re keeping the cinnamon roll warm for her. [Los Angeles Times]