Open science (OS) where research planning, processes, data and results are freely available to all stakeholders is the future of science. OS will make science more effective and more responsive to societal needs, and it will enable citizens to participate actively in all aspects of science as citizen scientists. OS does, however also raise new questions about research ethics, integrity and misconduct. We know that research misconduct and questionable research practices occur in our current scientific processes, and it is likely that similar or new forms of misconduct and questionable practices will emerge in OS. It is therefore important to identify and analyse the potential for misconduct in various areas of OS practice and in different scientific disciplines, and to identify and analyse current ethical, social and legal approaches to responding to questionable practices. It is only based on such an analysis that the European science system can effectively ensure that ethics and research integrity (ERI) becomes a structural component of Open Science. ROSiE will provide this analysis and develop practical tools aimed at ensuring ERI in OS and citizen science (CS). This will be done by a strongly multi-disciplinary project group consisting of world-leading experts and organizations in OS, CS, and ERI. We will: EXPLORE: Provide a systematic inventory of ERI, social, and legal implications and challenges of OS; and of existing technologies and platforms that safeguard responsible OS. ENGAGE: Conduct consultation and stakeholder engagement aimed at creating and sustaining a community of practice involving all European stakeholders interested in OS and ERI. GUIDE: Conduct a strategic policy assessment for promoting responsible OS and develop operational guidelines for relevant stakeholders, including a complement to the European Code of Conduct for Research Integrity. EQUIP: Develop an ERI knowledge hub for OS and training materials for ERI aspects of OS.