Not to be confused with the essential oil of Rosemary, ROE is used as an anti-oxidant in formulations. Use at .02 - .05%. It should be a dark brownish green thick liquid. If you are getting a thin oily product, then it is not pure ROE.
We have recently discontinued distributing Grapefruit Seed Extract (GSE) in favor of Rosemary Oleoresin and Black Willowbark Extract. In recent testing, GSE has not been demonstrated to be an effective preservative and anti-oxidant. While the benefits of GSE in some cosmetics are debatable, it has been clearly shown that GSE cannot stand up to the high pH levels created in soap making, and after a short exposure to pH 7.9 or higher, GSE begins to break down and it's preservative and anti-oxidant properties become negligible.
Rosemary Oleoresin has been demonstrated to have anti-microbial characteristics. Rosemary Oleoresin can be used in concentration as little as 0.1% and some sources state that 4 to 8 drop per pound of soap, or .02 to .08% to any base oil is sufficient for protection without having to worry about SAP value issues.