Roo is a rapid application development framework for Spring and Java that allows for domain-centric design of database entities, auto-scaffolding of UI elements, and generation of a full stack Spring web application. It provides an alternative to non-Java and non-Spring convention-over-configuration frameworks. Key features include generating entities, relationships, controllers, and basic CRUD UIs through its command line interface. Aspects are used to wire together the generated code and framework features.