The emerging System-of-Systems (SoS) concept describes the large scale integration of many independent self-contained systems to satisfy global needs or multiple requests. The increasing number of interacting (mostly embedded) systems in our strongly connected society and industry as well as the growing overall complexity of systems have triggered a paradigm shift and the need to enhance the classical view of Complex System Engineering towards SoS Engineering. SoS find their application in many highly relevant areas to our society: air-traffic control, urban transport, smart grids and integrated multi-site production, among others.The inherent complexity of SoS as well as the need to meet optimised performance for both the individual systems and SoS, raise many questions which are the object of important research efforts nowadays.The project Road2SoS will develop advanced research and engineering roadmaps to identify future RTD and Innovation (RTD&I) strategies for Europe in the field of SoS Engineering in four key domains:•\tDistributed energy generation and smart grids•\tIntegrated multi-site industrial production•\tMulti-modal traffic control•\tEmergency & crisis managementThe roadmaps will comprise the latest high-level scientific results and will identify trends in research and development and associate them to future product and application visions.They will also be integrated in the socio-economic context, via workshops and case studies in order to facilitate the transfer and integration of European RTD+I results and developments from the SoS Engineering sector to relevant stakeholders.The project will help European organisations to stay at the front of these new developments and to be prepared for future challenges in the industrial applications of SoS in order to reinforce the leading position of the European industry in Complex System Engineering.