Although it is clear that Jane does literally save Rochester's life in a physical way (he needs help now that he has suffered tremendous injuries), it is important to note that his true salvation comes in the form of his recognition that Jane is his equal; Blanche Ingram never would have been his savior. Also, the fact that Rochester was blinded by the fire but then regains his sight when Jane returns to him could also be related to his salvation. Figuratively speaking, he is able to see more clearly when she is his partner in life, whereas prior to this, he is blinded by a commitment to Bertha.
At the end of the novel, Jane returns to Rochester. She is shocked at his appearance and finds that he has been left blind and one of his hands is amputated because he was severely injured trying to save Bertha Rochester during a fire. He now resides at Ferndean, about 30 miles away from the blackened ruins of Thornfield. Jane arrives, and, as they talk, Rochester "stretched his hand out to be lead, I took the dear hand. . .I served both for his prop and guide." Thus, Jane's return probably saves Rochester's life because he now has someone to support and even guide him. Eventually, she marries Rochester and they have a child. Even though she is considerably smaller than Rochester, they have become equals in strength of character and intellect.
Jane literally saves Rochester's life when she woke him when his bed is on fire. She woke him by throwing water on him while he was asleep. His wife, Bertha, had escaped from her secret living quarters and set his bed on fire.