According to the British Society for Cell Biology, rough endoplasmic reticulum is studded with ribosomes. Rough ER is a cellular membrane-bound organelle involved in protein production, protein folding, quality control and protein dispatch. Rough ER is contrasted with smooth ER, which does not contain ribosomes and serves a separate function.
Molecular Expressions from Florida State University describes ribosomes as the protein production machinery of the cell. The rough ER and its bound ribosomes take polypeptides and amino acids from the cellular cytosol and continue protein assembly.
According to the British Society for Cell Biology, some of these proteins are shipped into the lumen of the rough ER, while others stay adhered to the ER membrane. Membrane-bound proteins are ultimately incorporated into the plasma membrane of the cell. Proteins in the lumen are folded for a specific functionality and undergo a quality control checkpoint. The proteins are then shipped to the Golgi apparatus for final packaging and delivered to their intended location.