Besides packaging secretory proteins into transport vesicles, what is another major function of the rough er?

Another major function of the rough endoplasmic reticulum (ER) is that it separates the secretory proteins from proteins that are formed by free ribosomes and they remain in the cytosol.

Rough endoplasmic reticulum is a structure made up of highly convoluted blocked sacs. The rough endoplasmic reticulum is covered with membrane bound ribosomes. It is the center where membrane is produced for the cell and it is associated with protein arrangement, protein production, and quality control. The rough endoplasmic reticulum functions with the membrane bound ribosomes by conveying polypeptides and amino acids from the cytosol into transport vesicles.