It doesn't matter. It never mattered. Whoever she was with, whatever she felt, wherever she was… it didn't matter.
The Doctor didn't want it to matter.
If it mattered, it meant he would have to be hurt. That meant that every word he spoke, every step he took, and every breath he gasped would all be for her.
The Doctor didn't want it to matter because it was too unbearable to matter. Rose was gone. She is gone and it cannot matter. She has her own Doctor, her own life, and the new new new Doctor wasn't a part of that.
So it didn't matter, not to him, because even someone as strong and forever as a Timelord couldn't handle that. The eleventh Doctor took solace in the fact that it didn't matter and never would.
Even if somewhere in the back of his mind… he knew she was all that mattered.