There is currently a lack of Requirements Engineering (RE) approaches applied to, or supporting, the development of a Domain- Specific Language (DSL) and the environment in which it is to be used. We present a model-based RE approach to support DSL development with a focus on usability concerns. RDAL is a RE fragment language that can be complemented with other languages to support RE and design. USE-ME is a model driven approach for DSLs usability evaluation, which is integrable with a DSL development approach. We combine RDAL and a new DSL, named DSSL, that we created for the specification of DSL-based systems. Integrated with this combination we add USE-ME to support usability evaluation. This combination of existing languages and tools provides a comprehensive RE approach for DSL development and an interesting case study of languages composition allowing the reuse of the assets of the existing languages. We illustrate the approach with the development of the Gyro DSL for programming robots.