Hi There! :)
Without the rough ER, cells would ?
The endoplasmic reticulum serves many functions thus without it all those functions would vanish leaving the cell incapable to manage properly resulting in death. The endoplasmic reticulum is divided into the smooth and rough endoplasmic reticulum; both vary in function. First, the smooth ER serves as a structure which catalyzes foreign substances to make them less harmful, i.e. detoxification. The rough ER serves as a structure which performs protein synthesis.