I've only played through with 1 character. No bugs as far as I can tell, romance and ritual intact. Aside from what Tale said, Morrigan reveals that the boy "is an innocent, he has no idea what destiny lays before him". She eventually has to leave, you can convince her to take you with her in which case she will say "you... you cannot know what you ask. It would be better for you, better for us if you stayed" insist "very well my love, we will face the future together" and you both leave. It was a good ending to Origins I think but very much open ended, deciding where and what role your Warden will have in the sequel I guess (could have done without the 4 dungeons preceding it tbh, would a DLC that was nothing but conversations and story have been so bad?).
An alternate to leaving is to stay, in which case Morrigan will point you to the elven book laying on the ground near by, tell you to read it for answers and then you get a cutscene of her leaving, you picking up the book and walking away -credits.
A third alternative is pretty brutal. You can say you're here to kill her, which with the history the two had she won't really believe. She'll say the same stuff about the child, Flemith ect. When she asks if the conversation is over you can attack her. Cutscene of the warden stabbing her in the stomach, her looking betrayed and horrified and falling back through the mirror. You collect the book and leave. That one will come back to haunt the warden later I expect.
There are probably more outcomes but those are the three I found.