I can agree there, scotpens. It's sad the differences aren't taught...perhaps kids are too busy worrying about Instragramming or tweeting every fleeting thought on their iPhones or listening to "One Direction" to worry about things like grammar or punctuation.
A role in a play is different from rolling while at play. You incite a crowd, but have an insight into why the crowd does something. Dictionaries are useful, and you can then find out why words are the way they are, and where they came from (or perhaps 'whence they came' to avoid ending with a preposition).