Bee insulted one individual based on her perception of how that one individual conducts herself. It was a crude remark. Roseanne insulted an entire race of people - two races/ethnicities, really - while attempting to insult one person. And the insult wasn't even mostly based on how that one individual conducts herself; it was based on her genetic makeup and heritage.
Bee was commenting in response to a social media post by Ivanka that she, and/or her writers, perceived as insensitive and calculated. Roseanne was tweeting in response to.... what?
Both Bee and Roseanne knew what they were saying/typing. The 'off-the-cuff' defense is not a suitable defense for Roseanne. Bee's audience is primarily composed of people who would, more or less, tend to agree with her opinions. She's not on network tv and the comments didn't/haven't/won't likely negatively impact viewership. From a business standpoint, assuming her ratings were good prior to the remark, it wouldn't make sense to fire her. Roseanne's show reaches a larger, more diverse audience that watches more for entertainment value than for social commentary. With her tweet, she alienated a pretty significant portion of the show's audience. From a business standpoint, a severe punishment was warranted.
If somebody at Fox News levied a personal attack on Hilary Clinton, similar to Bee's comments - without the c-word, obviously - would Conservatives expect backlash from the Left but, more or less, tend to agree with the criticism? Yeah, probably. Would anybody expect the Fox News person responsible for the remarks to be fired? Probably not. At least, 90%+ of the viewers of the program wouldn't want or expect it. Bee's situation is the same, just from the other perspective.
Bee hasn't shown any history of racist thoughts. Her husband opposed re-zoning of NYC schools back in 2016 for various legitimate reasons, as many parents would, none of which were based on race. Nice try, though.
Bottom line, being impolite and mean to a single person because you don't like them or what they have done/do is different than slamming entire cultures or ethnicities as a basis for putting down somebody you don't like.