In terms of the Doctor's timestream, he (as the Ninth Doctor) first met Rose in the basement of Henrik's department store, when he rescued her from some Autons -- a favour she returned not long afterwards ("Rose").
As the War Doctor, he had previously encountered the likeness of Rose (but not Rose herself) on Gallifrey on the last day of the Last Great Time War, when the interface of the Moment, having confused his future meeting with Rose for a past encounter, adopted Rose's appearance to interact with him ("The Day of the Doctor"). Because of the circumstances, he didn't retain his memory of what the interface had looked like.
In terms of Rose's timestream, he (as the Tenth Doctor) had met her outside her block of flats on the Powell Estate in the early hours of New Year's day ("The End of Time", part 2), a couple of months earlier than their meeting in Hendrik's. He was careful not to let her get a good look at him, so she'd not recognise him when she later saw him regenerate into that incarnation.