At least not in the Eleventh episodes, can't speak about any others though. I simply assumed they had appeared in the past. Or maybe they will do so in the future?

I also don't think Rosto's the fiancé in question, that would be too.. I don't know, abrupt. I think there might be some more stuff concerning Rosto in the future, she has somehow given an impression of building up the character, and it would be a bugger if all of that potential would be left.
I am a fan of Beka/Rosto, but I don't know if they would really do well..