Thinking more about this, what if Lilith needs to be in Heaven as a sort of asylum to keep her away from someone in Hell? What if Rosie needed Lilith for something she wanted no part in, explaining why both she and Alastor disappeared around the same time?
Hey so what do you think the chances are that the deal Lute mentioned was for the exterminations? It's interesting how the only people who seem to know that Lilith is in Heaven are Lute, Adam, and Sera, who were all involved with the exterminations in some way