Mixing up role and roll is a common mistake. Role is a noun, but roll can be a verb or a noun. You can find more comprehensive definitions of roll – I’ve just listed the main uses here (it’s a really long list otherwise) – but mine should give you an idea of the difference between the two words.
Role
- a task or function
Roll
to move by turning over and over; to rotate- to move or run on wheels
- to turn something over and over to form a ball or cylinder
- to flatten something
- to reverberate; a prolonged reverberating sound
- to appear like waves; to undulate
- something that has been rolled up to form a cylinder shape
- a small bread (enough for one person)
- an official list or register
- a swaying or unsteady movement
My tip: associate roll with ball (balls roll and you can roll something pliable into a ball) and/or poll (you need to be on the electoral roll to use a polling station).
Sources:
Hannah McCall 
That should be AN eye roll! 😀
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I see this mistake so often. I can only comment with en eye “roll.” 😀
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