Both the smooth and rough endoplasmic reticulum help in the production and storage of proteins The main difference is that one contains ribosomes on it and the other does not.
The rough endoplasmic reticulum (RER) has ribosomes on its surface. This is what give the RER a "rough" appearance. Rough ER looks like sheets.The RER synthesizes (makes) and packages proteins. The RER is attached to the nuclear membrane. The Golgi apparatus tends to be on the other side of the RER.
The smooth endoplasmic reticulum (SER) does not contain ribosomes. The Smooth ER looks more like tubes. The SER helps in the storage of proteins and lipids. Cells that produce oils have a higher ratio of SERs than do other cells. The smooth endoplasmic reticulum can be found dispersed throughout the cytoplasm of the cell.