Other mistake: When the opening credits are shown, the door to the basement is in the kitchen. In the beginning of the series the door is still in the kitchen, but in later seasons the basement door is in the laundry room, but in the opening credits it is still in the kitchen.
Suggested correction: I had noticed the same thing and thought it was a continuity mistake. However, in Season 3, Dan mentioned building the back service porch where Roseanne does the laundry. There are two basement accesses, the one in the kitchen, and what was probably the outside entrance in the backyard that is now enclosed inside the service porch. The family prefers using that one. Most houses, mine own included, have multiple basement access, one inside the house and one outside. In my state, it's a building code requirement.
Continuity mistake: In one episode, there is a bowl of fruit on the table in the living room. The boys start wrestling and they knock it down. In the next shot it's back on the table again, untouched.
Continuity mistake: During the show's first two seasons, we are told Roseanne had a more slender figure during her younger years and didn't start gaining weight until after she began having kids. Later in the Halloween episode, "The Ghost of Halloween Past," Roseanne is shown her past, and her younger versions are not slender.
Continuity mistake: In episodes when Darlene has just moved into her apartment, the bathtub is on the wall in front of the bathroom door. In later episodes, the tub is on the wall to the left of the door.
Continuity mistake: In "Guilty By Suspicion," Jackie hangs up her coat in her living room closet. This is the same door that, when she first moved into the house, led to the basement.
Continuity mistake: In the episode where Jackie takes over the house, while Roseanne is at their parents. DJ comes in the kitchen and is sent in the laundry area for a shirt. Before he goes in there he is wearing a pair of dark jean with nothing on them. He comes back a second later with his head stuck in a shirt still with the same pants on. But when he finally pops his head through the shirt his pants have changed to a pair of stonewash, with what looks like bleach stains on the front. A wide shot of the kitchen in the next frame and his pants are back to the dark ones with nothing on them.