This contribution explores Gilles Personne de Roberval’s 1644 Aristarchi Samii de mundi systemate, partibus, & motibus eiusdem, libellus. I focus on the complex circumstances of publication, the intellectual context of the polemics of Copernicanism within the scientific community, as well as the natural philosophy of the treatise. Roberval’s strategy of publication provides a very sophisticated example of authorship in early modern natural philosophy. The strategy lies at the conflux of certain specific motivations. I contextualize these motivations by accounting for the delicate debates around the motion of the Earth in mid-seventeenth century Europe, the institutional communities of the Collège Royal and Mersenne’s circle, and the disciplinary bounds of Roberval’s professional authority. Weighing in all the elements, I argue that Roberval’s publication is an interesting intellectual game, playing with the notion of ancient authority and humanistic recovery. By this somewhat libertine attitude, Roberval takes a stance in a complicated debate around heliocentrism and the status of hypothetical cosmology. Roberval’s position is supported by his natural philosophical speculations, which I situate in the contemporary debates of the community. Roberval borrows from many philosophers, but he aims at achieving a highly systematic speculative cosmology. One of the functions of this system is to confirm Copernicanism, while maintaining a very pessimistic attitude on the prospects of precise astronomical knowledge and, among others, prognostication issues.