The way the 9th season should've gone down
Just my two cents - John Goodman didn't want to do the entire season so this would make sense (although feminist Roseanne probably would've never gone for this idea):
After Dan and Rosey's fight at the end of season 8, they make up but things are still tense. Then Dan has another heart attack and this time he dies. Season 9 would be about Roseanne's struggles to hold everything together.
During times when Roseanne would be bummed out, 'Dan' would appear to her and encourage her or say something to anger her so she'd get her fight back on.
She could also talk to 'Dan' when one of the kids was having problems. He would be there for the birth of his grandchild and other events where he was needed.
The final episode could be about Roseanne opening up to everyone about how she was going crazy because she keeps seeing Dan like he was really there. She tells them that she has full conversations with him. Then she finds out that 'Dan' has been visiting all of them. She realizes that he has been their guardian angel.
'Dan' visits Roseanne one more time - to tell her that he's moving on and so should she. She's strong enough to make it without him. She was always the strong one. He was the one who needed her, not the other way around. Roseanne tells him he's wrong - she needed him too. But she confesses that he's right about one thing - it's time for her to move on.
In the final scene, Roseanne meets a nice new man - a regular working-class guy like Dan. There's a sign of hope that she could find happiness with a new love in her life.