The joint ISRR11/Rooting2021 online event brought together a multidisciplinary range of root researchers eager to hear about the latest technological developments and to discuss the most pressing research questions in the field. The meeting hosted the third ISRR Ambassador programme, which provided early career scientists from all over the globe with training activities and networking opportunities. Throughout this report, we have highlighted recent advances in root and rhizosphere research that were presented at ISRR11/Rooting2021. These advances cover a variety of scales (from molecules to ecosystems) and include a wide range of approaches, such as root phenotyping and mathematical modeling. This report also describes the results of a survey conducted by the ISRR Ambassadors to better understand how and why scientists use root phenotyping in their research, and to identify the main limitations they currently face. By identifying emerging research frontiers, such as the need to relate plant traits to their ecological functions, we aimed to provide scientists interested in the hidden half of plants with a roadmap for future research to further our understanding of roots and rhizosphere processes.