As with all opinion pieces, you will have to write this from your own perspective.
Hughes's story is so powerful because it contains a "life lesson." Our lives can be changed through one encounter. Roger did not intend to find one of these lessons, but it found him in the form of Mrs. Luella Bates Washington Jones. Mrs. Jones teaches Roger about compassion, discipline, and self- management. Through a random encounter, life lessons are revealed to both Roger and the reader.
I think that this might be a good starting point. Think about moments in your life where you encountered someone and you learned something about yourself, your world, and your place in it. Most of these life lessons are not sought, but rather thrust upon us. Reflect on instances that might not have seemed important at the time, but rather dawned upon you as very important. Sometimes, they come in the form of casual encounters, something brief which resonates in our minds. If encounters don't work, think about people you went to school with when you were younger and how some memory of them might have taught you something. The importance of friendship or the need to not lose touch with other people over time might be two examples of how encounters can yield life changing experiences. When you write your essay, think about how this encounter impacted you over time. The very fact that you are writing about it now shows its importance. Hughes's short story reminds us that life's lessons are sometimes the ones that take us by surprise and linger in our mind. Your essay might strive to communicate the same.