Hypothetically, if I was running House of Cards I would've fired Spacey and tried to hire someone like Bryan Cranston to replace him. The show is now going to have one final season and I'd guess Claire, his wife, is going to be the main character, which doesn't sound nearly as interesting.
For Roseanne, if possible, killing off her character would've been interesting instead of killing off the entire show, since the actors, writers, camera men, etc didn't do anything wrong and shouldn't be punished, only her. At worst, everyone would've watched the season premiere to see how they handle her death then stop watching, but since John Goodman is such a good actor, I don't see why he along with the family couldn't at least attempt to carry the show. It's not a show I watch so what do I know, but that sucks for the people losing their jobs.
I'm curious how others think similar situations should be handled.