In her last episode, "Doomsday", Rose is helping the Doctor in trying to close a void connecting our universe with a parallel universe (where Mickey had been trapped in an earlier episode and also where a version of Rose's father had survived, but her mother hadn't). Cybermen had come through the void from the parallel Earth to take over ours - as they're want to do - and it is revealed that the Daleks had hidden in the void and used the opportunity the Cybermen had presented to escape and take over the Earth and, subsequently, the universe. In the process of trying to close the void, and suck all of the Cybermen & Daleks into it, Rose loses her grip on the device needed to close it, and falls into the void - until her father from the parallel Earth appears to save Rose and take her back with him to the parallel Earth using a device they had developed to fight Cybermen. By closing the void, the Doctor made it impossible to visit that parallel universe and to see Rose ever again.
It is assumed Rose lives out a full and, somewhat, happy life. Her parents are reunited and even start a new family. She's back with Mickey but, of course, is still in love with the Doctor.
It was one of the best, and saddest episodes I've ever seen. OK, kind of long, but hopefully answers the question =)