Well, I finished my playthrough with my mage Roland (Roland started out as my main character but decided to finish with my male noble Arturo to get to the good stuff with Alistair). Thing is, even after turning down Morrigan and declaring I would make the ultimate sacrifice, Alistair
still sacrificed himself.

First he broke up with me after I made him king and then shortly before his sacrifice he tells me how much he cares? I couldn't stick around Ferelden after that. I told Queen Anora that I would be traveling for a while. I ended up going with Zevran and Sten back to Sten's homeland.
I did a game save right before the Archdemon battle so I may try again to see if I can still make the ultimate sacrifice. For the record, the party consisted of Alistair, Wynne, Zevran and myself (Roland). Alistair had not been hardened after his meeting with Goldanna so I'm thinking as long as A) Morrigan's offer is not taken and

he's in the party he will always die
Any comments, suggestions and/or hints would be most appreciated. Muchas gracias!