Who did Rodin use as his models? People he knew or just from memory?
Rodin did sculpt people he knew personally, including his long-time companion Rose Beuret, whose body was the model for many of Rodin's female figures.
He was also interested in the professionally trained body and hired dancers and athletes to pose in his studio. Sometimes when he wanted to sculpt the portrait of a deceased person, he would try to find a living model that resembled them. For example, when Rodin won the commission to make a monument to Balzac, he traveled to the writer's hometown to find a man that resembled him!
Did he ever do a sculpture of himself?
I know that he drew self portraits of himself. One scholar has argued that one of the sculpted figures for the Gates of Hell is a self-portrait, although I think that is open to debate!