This is a difficult prompt because several key characters in Khaled Hosseini's The Kite Runner display an alarming lack of courage much of the time. Since courage can be defined both by what it is and what it is not, perhaps a quick overview of the characters and how they did/did not display courage will be the most helpful to you. But in terms of how Hosseini "reveals the role of courage in shaping the individual," this lack of courage early on works to illustrate how characters are shaped by the courage they do not have, the courage they do have, and the courage they eventually learn to have.
Amir lacks courage in almost every way when he lives in Afghanistan. He is a boy who will do anything to win his father's fleeting approval, including allowing his friend to be raped by a bully. He says of himself:
I actually aspired to cowardice, because the alternative, the real reason I was running, was that Assef was right: Nothing was free in this world. Maybe Hassan was the price I had to pay, the lamb I had to slay, to win Baba.
He feels so much guilt that he commits another cowardly act and gets rid of the source of his guilt by forcing Hassan to go against his own nature and lie. Amir knows Hassan loves him more than Hassan loves himself, and he takes advantage of that. He is not a good friend in any way to Hassan unless it suits him, and he often shows despicable cowardice when he both fails to defend him and adds his own abuse. Even his father believes Amir is a coward as he says this about his son:
“I actually aspired to cowardice, because the alternative, the real reason I was running, was that Assef was right: Nothing was free in this world. Maybe Hassan was the price I had to pay, the lamb I had to slay, to win Baba.”
Amir finally shows some courage in America, but it is not until Rahim Khan calls and gives Amir the opportunity to make things right and assuage his guilt that Amir really demonstrates courage. He goes back to an unfriendly place and squares off with Assef, by then a powerful Taliban official, to rescue Hassan's son. He even brings the boy back to America, something he had not intended to do. We can see that things are going to be difficult for him, but Amir's most courageous days may be ahead of him.
Baba is not a man of courage, either, until he leaves Afghanistan. He is rich and self-righteous, and he does not practice what he preaches. He fathers a child with the wife of his dear friend, knowing Ali had to have known the truth. He is perfectly willing for his illegitimate son to grow up as a lower-class citizen and live in the servant's quarters behind his mansion, but he will not publicly acknowledge the relationship. When he does things for Hassan. Baba is only doing his duty; he is to cowardly to do more. As soon as things get difficult, Baba leaves Afghanistan.
On the other hand, Baba displays a lot of courage once he is forced to make a new life in a new country. Even in death, Baba does his duty by Amir and is an admirable character in the last years of his life.
Assef is a coward from the beginning of the novel to the end, and he demonstrates that by abusing (such a gentle word for his horrific behaviors) people who cannot fight back. That is cowardice.
Hassan, Ali, and Rahim Khan are noble characters in every way, and you should have no trouble thinking of examples of courage for them. A simple discussion of Hassan would be a powerful demonstration of courage in every way, especially forgiving after he was so cruelly mistreated by his friend.
The key to your speech will be organization. You can organize by character, by kinds of courage (physical, moral, emotional), by what courage is not, or anything else that makes sense to you.