Abstract: In this roadmap article, we consider the main challenges and recent breakthroughs in understanding the role of carbon molecular nanostructures in space and propose future avenues of research. The focus lies on small carbon-containing molecules up to fullerenes, extending to even larger, more complex organic species. The roadmap contains forty contributions from scientists with leading expertize in observational astronomy, laboratory astrophysics/chemistry, astrobiology, theoretical chemistry, synthetic chemistry, molecular reaction dynamics, material science, spectroscopy, graph theory, and data science. The concerted interdisciplinary combination of the state-of-the-art of these astronomical, laboratory, and theoretical studies opens up new ways to advance the fundamental understanding of the physics and chemistry of cosmic carbon molecular nanostructures and touches on their wider relevance and impact in nanotechnology and catalysis.