They are both part of the endomembrane system. When a cell

They are both part of the endomembrane system. When a cell makes it starts by transcribing RNA from the DNA located inside its nucleus. RNA is then carried out of the nucleus into the rough endoplasmic reticulum. There the RNA meets up with a ribosome which are attached to the ER. Though the process of Translation the endoplasmic reticulum makes polypeptides which then fold into the proper shapes to make proteins.https://answers.yahoo.com//index?qid=20101110202906AAAPb4n