The current drivers' championship leader told BBC Sport: "It is awesome at this track, it is one of the most special tracks of the year. It was not quite as difficult out here as some other occasions because the conditions was pretty much always intermediates.
"I am really happy, the car was handling well. Together with my engineers we fine tuned it perfectly and got there in the end. It is only qualifying, a long race tomorrow but I am very happy.
"Eau Rouge I was feeling good through it, really going for it and maybe that it where I made my time."
It is the first time that Rosberg has been the pole-sitter at Spa in his Formula 1 career.