https://classicbells.com/soap/ROE.aspIn its pure form, it has an intense smell of rosemary, that is, however, only slightly noticeable when dissolved in oils (or at HP cooking), but absolutely nothing of the smell survives saponification. Dosage is ridiculously low (drops per kg oils/fats).
You get it at many cosmetic suppliers. I've got a 50 mL bottle that probably lasts for my whole life. I diluted it 1:10 for it to be measurable at all.
ETA: Btw, the ROE concentrate is the only soaping ingredient that I have put into the freezer. I store high-linoleic oils (poppy, flaxseed, paprika kernel, pumpkin, sesame) in the fridge, but I try to not have too many in house at a time. I store lauric oils (babaçu, palm kernel), high-oleic oils, and hard fats at room temperature.