"Mount Rosemont lay about two hundred kilometers to the southeast, and was the largest and most spectacular volcanic mountain of the scattered chain anchored by Kareenburg’s hollowed-out peak."
―The mountain[src]

Mount Rosemont was a volcanic mountain on Sergyar named for Reg Rosemont of the Betan Astronomical Survey.

The initial survey of the planet by the Betans was located on the side of the mountain; when they were attacked by Barrayaran soldiers, he distracted the soldiers to allow his colleagues to flee. He was killed, but they succeeded in their escape.