Depending on the use area of rosemary essential oil, pharmaceutical, cosmetic, or in food, the choice of both method and extraction time is fundamental, and the sample characterization is mainly based on comparing a few compounds that act as markers of a defined quality for a precise application. In the present work, the kinetic study of major components of Rosmarinus officinalis L. essential oils obtained by solvent-free microwave extraction (SMFE) and by hydrodistillation (HD) has been followed in order to determine the optimum extraction time of a defined bioactive molecule or its chemical family as well as its recommended extraction technique, either SFME or HD. The monoterpene hydrocarbons were nearly extracted completely in the first instants by SFME and progressively by HD. In contrast, the oxygenated monoterpenes were substantially extracted during the first minutes by HD and progressively by SFME. While the extraction of trans-caryophyllene was achieved at the beginning with SFME, it required more than 2 h with HD. A substantial gain in the extraction time has been obtained using SFME. Even though the essential oils extracted by SFME (30 min) and HD (3 h) are qualitatively similar, the oil fractions obtained during extraction time are very different.