For a long time, during both the Doctor's ninth and tenth regenerations, Rose traveled around with the Doctor and even grew to love him.
Tragically, during a battle with the Daleks, Rose was pulled into and trapped in an alternate dimension and could not get out. It seemed the Doctor had lost her forever.
But when the Angels defeated Galvatron and the Cosmic Heart restored the Multi-Universe to normal, gateways to alternate dimensions were broken open, allowing Rose to get free and be reunited with the Doctor on newly-restored Gallifrey.
To Rose's delight, Princess Emily sentenced that the Doctor should have an extra companion with him...that being Rose. The Doctor was overjoyed to have Rose back and to finally be able to tell her that he loved her.
The Protectors of the Multi-Universe
Rose is still with the Doctor and Ebony and aided them in looking after David, Abigail and Olivia. She has also been like a mother to Abigail.