Polypeptides made by ribosomes which attach to rER will go into the rER to form the tertiary structure. Those polypeptides made by free ribosomes usually stay in cytoplasm. So are there any enzymes in cytoplasm to help them to form tertiary structure?
There are several types of proteins that do this, all of which fall under the category of molecular chaperones. In particular, chaperonins such as GroEL/GroES complex in E. coli, sequester newly-formed polypeptides to allow them to fold their tertiary structure and avoid aggregation. Another widely studied class of these proteins are heat shock proteins (Hsps): these are involved generally in acclimating cells to stresses (such as heat), and some of these Hsps have been specifically implicated as chaperones. I'm a new user, so I can't post a 3rd link, but just google Heat shock proteins and you'll find plenty of information.