Roast and puree the plums. Preheat the oven to 350F; lightly spray the inside of an 8 by 8-inch casserole dish with coconut oil. Spread the plums out in the dish. Whisk together the rosé, honey, cardamom, and salt, and pour onto the plums. Roast 20 minutes, giving the plums a stir once halfway through. Cool to room temperature, and then puree the plums with their liquid. TIP: Taste and add more honey if desired.
Fill the popsicle molds. Pour the mixture into popsicle molds, making sure not to fill the molds over the “fill” line. (My molds are 2 1/2 oz/75 ml and I got 6 popsicles with just a little leftover.) Tap the mold several times on a hard surface to help any air bubbles escape.
Freeze. Transfer to the freezer, wait 20 minutes, and then insert the sticks. Let the popsicles freeze completely, about 3 to 4 hours, depending on the size of your popsicles and how cold your freezer is. To easily unmold the popsicles, dip the plastic bottoms in warm water and they should slide right out. Once unmolded, wrap each popsicle individually in plastic wrap and store in the freezer for up to 3 months for best flavor.
Notes
Storage: After unmolding the popsicles, wrap each individually in plastic wrap and put them into a gallon-sized freezer-safe zip-top plastic bag for up to 3 months. They'll be fine to eat after that, but they may not be as flavorful.