A description of the Roller Compaction process and the various process parameters that affect the quality of the roller compacted ribbons. Feed rate, compaction pressure, and roll speed are all discussed. Poor control of these parameters can affect Critical Quality Attributes (CQAs) such as tablet hardness, tablet or capsule weight, tablet friability, and dissolution rates. Ribbon density and porosity are also discussed as they affect both downstream processing and final product attributes, one of the most important being tablet dissolution rate. When implementing Process Analytical Technology (PAT), density and porosity measurement of roller compacted ribbons can help to ensure consistent output of the roller compaction unit operation. The process design scientist, working with formulators, scale-up personnel, technology transfer personnel, and manufacturing can use this in-process density and porosity check to ensure product quality, process efficiency, and reduce the chance of failure during product quality control testing.