Ribosomes are cell organelles that are responsible for the synthesis of proteins. Their function is to create proteins by linking amino acids together after reading the mRNA corresponding to these proteins in a process called translation.
These ribosomes are usually bound to the rough endoplasmic reticulum (hence the 'rough' in the name of this type of ER).
A large number of RER and ribosomes would indicate that the cell is primarily a protein-producing or enzyme producing cell. A huge number of ribosomes means that the cell is capable of producing more proteins compared to others.
As a concrete example, pancreatic cells have been found to contain more ribosomes and rough ER's than other cells. As you may know, our pancreas are responsible for synthesizing and producing some digestive enzymes and proteins for our body.