Do Alpha!Rose and Dave know Roxy and Dirk are coming? If so, how?
Yes, Seers have this weird thing of remembering their pre-scratch selves. The Signless remembered his life as Kankri and how better Beforus was and that’s why he started his movement. Similarly Alpha!Rose remembered Sburb and got Alpha!Dave involved in prepping for their ecto-parents to arrive centuries later.