This paper discusses the results of the RETHINK big Project, a 2-year Collaborative Support Action funded by the European Commission in order to write the European Roadmap for Hardware and Networking optimizations for Big Data. This industry-driven project was led by the Barcelona Supercomputing Center (BSC), and it included large industry partners, SMEs and academia. The roadmap identifies business opportunities from 89 in-depth interviews with 70 European industry stakeholders in the area of Big Data and predicts the future technologies that will disrupt the state of the art in Big Data processing in terms of hardware and networking optimizations. Moreover, it presents coordinated technology development recommendations (focused on optimizations in networking and hardware) that would be in the best interest of European Big Data companies to undertake in concert as a matter of competitive advantage.