The final season is markedly different from previous seasons and is ultimately revealed to be a fantasy of Roseanne's that she made up to comfort herself. Much of this was then undone when The Connors premiered. Roseanne is definitely an unreliable narrator.
Roseanne and Jackie were abused by their dad in the past and it is a topic that is brought up often. David is also abused by his mother in one episode.
About 11mins into the episode (right after Darleen runs upstairs to check on Becky) she finds Becky in front of the toilet bowl and the next 6mins basically there's alot of talk about being sick and imagery to match. You don't actually see anything happen and no noises that I could hear though I did have the volume turned down.