I am sending this info from FRENCH COUNTRY COOKING, Ann Hughes-Gilbey, 1983, Chartwell Books, Inc. 1994.
“Confiture des Baies de Rosier (Rose Hip Jelly)”
“Leave the hips, garden or wild, until after the first frosts; when they start to wither they will be softer and sweeter.
Top and tail washed berries and put in a kettle with a little water to stop them sticking. Bring to a boil, then simmer without stirring till very soft (45-60 minutes.)
Sieve (the seeds of some wild rosehips contain an irritant, so be quite sure to strain them all out). Put into a clean pan, with a little boiling water if the pulp is very thick. Cook gently for 10-15 minutes longer; strain through a cloth.
Measure this juice and add 1 1/4 cups sugar per 2 1/2 cups juice. Stir to dissolve; cook for 20 minutes, add grated lemon rind (approx. 1/2 lemon per 2 1/2 cups) and seal.”
I tried this last year with the rose hips from my garden, and it worked well. It is important to know that you should wait until the rose hips appear “withered,” until frost or late autumn.