The words role, roll sound the same but have different meanings and spellings. Why do role, roll sound the same even though they are completely different words?
The answer is simple: role, roll are homophones of the English language.
A character or part played by a performer.
The characteristic and expected social behavior of an individual.
A function or position. See Synonyms at function.
Linguistics The function of a word or construction, as in a sentence.
To move forward along a surface by revolving on an axis or by repeatedly turning over.
To travel or be moved on wheels or rollers: rolled down the sidewalk on their scooters.
To travel around; wander: roll from town to town.
To travel or be carried in a vehicle.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.
If they are spelled the same then they are also homographs (and homonyms); if they are spelled differently then they are also heterographs (literally "different writing").