I don't add ROE to commercial lard or coconut oil. The lard is partly hydrogenated and has additives to lengthen the shelf life. The RBO coconut oil is a shelf stable fat in my experience, and I don't keep large amounts on hand, so I'm not too worried about it. I add ROE to home rendered lard and tallow as well as to my liquid fats.
I microwave my fats to melt them. I microwave for a short time, stir to even out the temperature, and repeat until melted, so the fats heat up as evenly and gradually as possible.
I live in the UK and it seems impossible to find ROE. What they sell here is called rosemary seed extract (antioxidant). INCI: Helianthus annuus (Sunflower) Seed Oil, Rosemarinus officinalis (Rosemary) Leaf Extract.
Is this the same stuff as ROE? Can it be used in soaps?
Yes, it is ROE, and it can be used in soap. It sounds like you had to do some serious digging to figure this out!
I'm seeing some companies on both sides of the pond call it Rosemary Seed Extract even though it's not an extract of the seeds, but the key thing is the INCI and/or product info should say Rosmarinus Officinalis (Rosemary) Leaf Extract.
ROE is diluted to standardize its carnosic acid content -- I've seen ROE sold at 2%, 5%, and 7% carnosic acid. Since it's fat soluble, that's why sunflower seed oil is also in the INCI.