A massage oil is a carrier oil, sometimes with essential oils diluted into it. A gemstone roller is a polished stone on a spindle used on the face. They get sold together and they work together, but the useful information about each is quite different.
Carrier oils, and which does what
Sweet almond — the default. Medium weight, slow absorbing, good glide. The one to buy if buying one. Avoid with a nut allergy in the room.
Grapeseed — lighter and faster absorbing, less greasy on the skin, but it oxidises quicker so buy smaller bottles.
Jojoba — technically a liquid wax rather than an oil, closest to the skin's own sebum, and the most stable of the three. Expensive, and the one to choose for the face.
Fractionated coconut — very light, indefinitely stable, no scent of its own. Good for blending, less good for a long massage because it absorbs too quickly.
Dilution, properly
Essential oils are not massage oils. Undiluted essential oil on skin causes sensitisation — often not the first time, which is what makes it insidious, but on the tenth or twentieth exposure, and once sensitised it is usually permanent for that oil.
For body massage, 1–3% is the working range. That is roughly 6 to 18 drops in 30ml of carrier. For facial use, 1% or less. For anyone pregnant, elderly, or under about six, halve it and check the specific oil — several are contraindicated regardless of dilution.
Gemstone rollers
The cold is the point. Stone stays several degrees below skin temperature and holds it, which is why a roller feels better than a plastic one. It does not need to go in the fridge, though it will feel colder if it does.
What a roller reliably does is provide gentle mechanical pressure that can reduce the puffy look of fluid retention around the eyes, and it feels pleasant. Claims about lymphatic drainage being meaningfully changed by two minutes of rolling are considerably stronger than the evidence. Buy it because it is a nice thing to use in the morning.
Cleaning a roller
Oil residue plus skin means a roller needs washing, and the spindle is the part that traps it. Warm soapy water, dry immediately, and do not soak it — most rollers are glued at the pins and prolonged water gets into the joint. If the stone starts to feel gritty as it turns, the pin needs cleaning rather than replacing.