What kind of potions do you mean? There are the magickal kinds with magickal effects and there are the kinds for medical usage. I know the one for medical uses.
Medically rosemary can be used for cancer, depression, hair loss, high blood pressure, and memory loss.
Sorry, couldn't find much for basil.
Note: A medical potion is the same as making a tea out of the herb(s) except that you wiould leave the herb in the water a bit longer so that the properties of the herb can mix into the water.