Explanation:

- Ruskin Bond: The correct answer is Ruskin Bond. He was awarded the John Llewellyn Rhys Prize in 1957 for his novel 'The Room on the Roof.' Bond wrote this book at the young age of 17, marking the beginning of his illustrious writing career.

- Salman Rushdie: Known for books like 'Midnight's Children,' Salman Rushdie has achieved critical acclaim and won several awards, but not for 'The Room on the Roof.'

- Khushwant Singh: He was a prominent Indian author and journalist, famous for 'Train to Pakistan.' He did not write 'The Room on the Roof' and hasn't won the John Llewellyn Rhys Prize.

- Amitav Ghosh: Celebrated for his works like 'The Shadow Lines,' Amitav Ghosh is another esteemed Indian writer, but he did not author 'The Room on the Roof.'