fledgling
Good idea, Chiron! And the tart ones are good for gout (which is excess acidity, I believe).
I don't know about melatonin, but rosehips are great for Vitamin C.
Some used to make a lovely jelly from them (very 'gifty' but lots of work I would think). I only got around to sucking them. Some dry them for rosehip tea. (Whole? Crushed? Fresh?)
I searched and found no warnings about any varieties.
The only thing about rosehips is that the meat is thin, and the center is loaded with seeds and a kind of soft 'fur'...not too hard to handle, just spit.
Watch for sprayed bushes, of course. Good reason not to pick off your dead roses.
F.