Hi Melphone, I can't advise you about using it in conjunction with Rogaine as this is a new area to me, but in general you would use a pure oil. I like almond oil because it is light weight...olive is heavy and maybe difficult to remove. Almond, sunflower or plain old vegetable are just fine and you are looking at a teaspoon in total. I'm not sure why the healthfood place would recommend against using vegetable, tho thggis maybe to do with potential nut allergies. I can't think of any other reason, as it is as good as anything else. Some people like minberal oil too, but I find this a little too light weight.