I'm not sure pure rosehip oil can be extracted without the use of a carrier oil. I'm not positive, but I think you need to use "cold steam" and high pressure, which would probably require industrial equipment. Is there no oil you could use as a carrier? Sweet almond oil, or virgin coconut oil, perhaps?
The only reference I was able to find was this blurb from the International Society for Horticultural Science, but you have to join and pay a membership fee to access the article it mentions:
"After login you can download the full-text version of the following article:
ISHS Acta Horticulturae 690: I International Rose Hip Conference
ROSE HIP SEEDS ARE NOT WASTE
Authors: O. Ãƒâ€¡ınar, K.S. Dayısoylu
Keywords: Rosa, rose-hip, seed oil extraction, solvent extraction, supercritical extraction, yield of extraction
Rose hip seeds are generally wasted; that is, they are crushed and used for animal nutrition or burned in spite of their high value. In fact, the valuable oil can be extracted from these seeds and they can be used for medicinal purposes (i.e. against contact dermatitis and for its anticonflict action). In this study, several oil extraction methods such as traditional pressing, solvent extraction methods (e.g. soxhlet, ultrasound, microwave extraction with hexane), and supercritical fluid extraction are investigated for obtaining oil from rose hip seeds."