All direct descendants of Choral the Conqueror, save some claimed Bastards (who may have been lying about their claims) such as Roland Fitz-Rogarvia of the Fanged Legion, and members of other houses who married into the Rogarvian Royal Family disappeared.
As time has gone on, fewer and fewer people await the House's return, saying that some dark magic must have spirited them away. Rumors as to why the house has disappeared include:
Curse of the Conqueror: Choral the Conqueror's vengeful spirit wracked a horrible vengeance against his descendants for some imagined slight.
Dragon's Debt: In return for the Dragon's alliance, House Rogarvia's founder Choral the Conqueror pledged his descendants blood, hundreds of years into the future.
Planar Ascension: Given the goings-on at Skywatch on the day of the disappearance, some theorize that the House teleported itself to another location-- or was ripped there by Demons or magic like that which created the Wasted Lands.
After the Disappearance, Skywatch sealed itself and although signs of lie, such as the occasional puff of smoke, or loud clanging sounds can be heard without, the entire tower-citadel has gone into lockdown. Raiding parties led by House Orlovsky have been unable to breach its walls.