Domain-specific modelling languages (DSMLs) successfully separate the conceptual and technical design of a software system by modelling requirements in the DSML and adding technical elements by appropriate generator technology. In this paper we describe the roles within an agile development process that allows us to implement a software system by using a combination of domain specific models and source code. We describe the setup of such a process using the MontiCore framework and demonstrate the advantages by describing how a group of developers with diverse individual skills can develop automotive HMI software.