Also check https://www.researchgate.net/publication/284222289_Influence_of_Drying_Methods_Extraction_Time_and_Organ_Type_on_Essential_Oil_Content_of_Rosemary_Rosmarinus_officinalis_L
Extraction of essential oils better for leaves around 45° and inflorescences around 35°( depend of the plant morphologyas well). If you dried at 70° you might get some oil but if you are looking to quantify the content and quality I would recomend to dry in lower temperature.