I made rosehip syrup with that type. I wondered what type of rose they were. I have notice a few types of rosehip including a black one of simerlar fat shape. Removing the seeds on R.rugosa is really difficult, the seed hairs are like fibre glass so I just make syrip with them as then I dont need to deseed.
Take eoungh rosehips to to 3/4 fill a large saucepan.
Cover whole hips with water.
Simmer until hips are squishy.
While wearing gloves squeeze through net bag, then repeat to ensure all seed hairs are removed.
Add about four handfuls of sugar for every pint of liquid.
Return to pot and simmer for ten minutes.
final product should keep for months and is nice on pancakes.
I dont measure when cooking so this is a rough guide.