If your rosehips are not already chopped, go ahead and chop them up carefully on a cutting board.
Place the dried rosehips in the bottom of your crockpot.
Cover them with the olive oil, or whatever oil you choose.
Set your crockpot to the lowest heat setting and let the rosehips and oil simmer away.
8 hours should do the trick.
Finally, take a fine piece of cheesecloth and/or a strainer and gently pour the rosehip and oil concoction through the cheesecloth.
Store in a dark bottle.
Notes
Remember to label and date the bottle. Rosehip oil will last up to 6 months when stored out of direct sunlight.Use the "keep warm" setting if your crockpot has that option.