Effectively, roots help you learn words related to a common theme and narrative. By learning the root of a particular word, you not only learn the word but also open up the possibility of learning multiple words using the same word root. This is the true power of word roots. If you use this well, you can build your vocabulary in the quickest possible time.
Knowing the etymology of a word provides enhanced perspective about its most effective use. You understand its original meaning and how it may have transformed over time, how people have used it past and present. You can differentiate subtle differences with similar or related words, both now and past.