The rough ER has ribosomes on it. The smooth ER doesn't.
Rough ER has Ribosomes embedded within it, and smooth ER does not.
Rough ER are covered with ribosomes and smooth ER are not. Also, the rough ER is against the nuclear envelope of the nucleus and the smooth ER is not.
Smooth ER aren't covered in ribosomes, but rough ER are. ER are like transport tubes that go through the cell.
No because if they been connected then it be smooth endoplasmic reticulum or the rough endoplasmic reticulum and it will be one of the both :p
And the nuclear envelope.