Roof of the World is a metaphoric description of the high region in the world, also known as "High Asia". The term usually refers to the mountainous interior of Asia, i.e. the Himalayas.

Which place is called roof of the world? Let's have some stream of consciousness first.
To answer the question, consider the following: The term usually refers to the mountainous interior of Asia, i.e. the Himalayas. So, the answer is the mountainous interior of Asia , i.e. the Himalayas.