yes, it was an ending that kept people talking for a really long time, and that is what the people that had it happen wanted to do. They were wanting something that would make a big deal in the world and that would get them viewers on things to come.
Rosanne was a very popular long running television sensation. The people who watched the show were loyal fans. When a show is that popular, it has to have a very climatic conclusion, to escalate it from being a great show to a historical one. This way watchers feel like they were apart of history and they didn't waste their years watching.
The final season was probably ill-advised for the most part, but that it ended up being a fantastical scenario was the most appropriate thematic finale for the show. It was not the best possible ending - the series should have ended earlier - but in context of the final season, it works.
I have not seen the ending to the show in a very long time, so it is a bit hazy. I remember they won the lotto and that they were happy and moved into some big fancy house. Other than that I am not sure what happened and how it was controversial? I liked the ending. How better of a happy ending can you get besides winning the lottery?
I do not think that the Roseanne show ending the way it did was the best possible ending to that show. I think that the idea that the Roseanne character was dreaming for a few seasons is such a dishonest way to write material for a show or series. That is why a lot of fans were angry.