Actually, I thought the way they handled the replacement was hilarious. If I recall the original popped in at least once and they made a joke out of having both in the same shot. (And of course she ended up coming back.) Roseanne had its ups and downs, but wonderful writing at its best.
And each of the characters, at different times, said to the original Becky --
"Where the hell have you been?" Funny stuff.
Fav all-time --
SOAP