In terms of socially, family dynamics, stereotypical home economics, and of course humor. Roseanne was a "black" show and The Cosby Show was a "white" show.
(Yes I know both Roseanne Barr and Bill Cosby are cancelled now and not respected by the public or mainstream Hollywood. Thats obviously fair and valid. Im just primarily talking about their shows back then)
Roseanne was way more relatable to your stereotypical black family than The Cosby Show was. And the humor was more relatable as well. Yes I know Bill Cosby originally made the show because he didn't like how most black shows back at that time always put them in a bad-light/bad rep I get that. But still, Roseanne in my opinion was better and funnier and again, more relatable.