Salt the grouse well and set out at room temperature for 30 to 45 minutes. Preheat the oven to 325°F.
Cut the root vegetables into chunks, coat with oil or butter and salt well. Let these roast while the birds come to room temperature.
If you're making the rose hip glaze, boil all the ingredients for it in a small pot until it thickens, about 5 minutes. Keep warm.
Put the herbs inside the birds’ cavities. Either smear soft butter over the grouse or coat with oil.
Take the roasting pan out and nestle the grouse, breast side up, among the roasting root vegetables. Roast hen sage grouse, prairie chickens or sharp-tailed grouse in the oven for 18 to 20 minutes, spruce grouse 15 minutes, ptarmigan for 10 minutes. Remove the roasting pan from the oven.
Set the oven to 500°F, or as hot as it will go. Baste the birds with a little more butter or fat. When the oven hits temperature, return the grouse to the oven and roast until the breast meat hits about 140°F at the thickest part, near the wishbone. This should take anywhere from 5 minutes for ptarmigan to 15 minutes for a big prairie chicken or sage hen.