So, a ribosome works a lot like a stock ticker and ticker tape. Many ribosomes, together with mRNA, will attach themselves to the outer membrane of the rough endoplasmic reticulum. Any proteins that those ribosomes make go into the inside of the endoplasmic reticulum, where it will probably go into a vesicle later. The vesicles will then bring the proteins to other organelles or even the outside of the cell.