Who is Rosa Cabarcas from Memories of My Melancholy Whores and what is their importance?

Rosa Cabarcas is described as a hard, experienced woman, who has been jaded by the things she has seen over the years. She is a madam of a small brothel that has been in business for many years. The narrator, once a regular visitor, has not visited the business in around twenty years. Rosa's brothel is housed in a group of buildings Rosa owns, which include a store that is a front for her business and to explain the great deal of money Rosa makes in her illegal business.

Rosa Cabarcas and the narrator have a relationship that is almost a friendship. They've both grown old and share a nostalgia for the past. Rosa treats the narrator with some preference because of their shared nostalgia, and she allows him to come and go from her business through a private entrance in order to protect him from being seen.