If you mean save as in not killing him at the very end, you can either choose to be killed yourself or you can do a ritual with Morrigan. If you mean not killing him at Landsmeet then you can either make him rule or if you spare Loghain, then make him leave.
Where we have been and where we are going are worlds apart -Raki- PSN: StalkerPizza
If you don't import a character or you start a character in DA:O then import it over to Awakening then yes Alistair will be rather blunt. That's due in part because:
You didn't complete his quest and became friendly with him, same with Wynne. If you complete your character's quests in Origins then you'll be able to be friendly to each other when you meet up in Awakening. At least that's what happened to me.
PSN: Gogetenks,360 Gamertag: CyborgGogetenks, Metal Gear Online: Magnius Member of S.O.I. (Sons of Immaturity/Idiocy/Irresponsibility) MGS4 4 Life!!!!