In the study, we examined in detail the effect of dehydrating using natural drying in the shade, convection drying, and microwave drying, which are the most widely used techniques, especially for tea and spices, both in practice and in theory, on the protein, and mineral composition of rosemary leaves. Also, we determined the color parameters, which are the reason for the selection because it creates the allure for spices. In microwave drying at 600 W, we obtained results close to fresh rosemary in all color parameters, especially brightness and greenness. Although natural drying, which does not have any energy and investment costs, is the second-best method in terms of color, 50 degrees C, which is the most common drying technique in the market, caused significant color losses affecting the commercial value of the product. We reached the closest protein and P, Ca, Mg, Fe, Zn, Mn, and contents to fresh products in dried ones at 600 W. In contrast, in K only, the highest measurement was at 200 W. Strikingly, we observed dramatic losses reducing the benefit obtained from the product regarding protein and almost all nutrients in both convective and natural drying techniques, the most common methods in practice.