Rosehips, Rosa canina L. (Rosaceae family), have been used for a long time for their beneficial effects on health, and they are largely exploited in the food and nutraceutical supplement sectors. The aim of this work was to apply and optimize for the first time the microwave hydrodiffusion and gravity (MHG) extraction of rosehips, as a novel application of solvent-free microwave extraction, previously conducted in a similar way only on mulberry, strawberry, and onion. The optimization was performed through a central composite design (CCD) by evaluating the effect of the experimental parameters on the yield; total polyphenol, flavonoid, and anthocyanin contents; radical scavenging activity; and content of vitamin C in the obtained extracts. As a result, the water moistening pretreatment was clearly revealed to possess a pivotal role in the quality of the rosehip extracts. Among the evaluated responses, the yield, the anthocyanin content, and the antioxidant activity were well described by the statistical model. Notably, the optimized MHG extract was compared with the ones obtained by conventional solvent extraction showing higher amounts of vitamin C, polyphenols, flavonoids, and anthocyanins, while the traditional extracts performed better in terms of yield. In conclusion, MHG represents a promising alternative to standard extraction methods for obtaining rosehip extracts rich in vitamin C and antioxidant compounds. In this respect, the results of our research support the employment of MHG on an industrial level for the production of rosehip-based food supplements enriched in vitamin C.