A gentle way to clean the rose seeds is to use a Cuisinart or other brand of blender with a dough blending attachment, which is made of plastic and does not have sharp blades. You can blend the rose seeds using this gentle dough attachment for several minutes without any damage to the seeds. Do not use a blender with sharp metal blades as damage to the rose seeds may occur.
Remove the seeds from the fridge. Try to do this around the time that the seeds would normally start to germinate, such as in early spring. Make sure that the environment outside of the fridge is about 70 degrees Fahrenheit. The seed will not sprout until you take them out of the fridge. Depending on the rose variety and individual seeds, the seeds could take anywhere from four to sixteen weeks to germinate. Often, 70% or more of the seeds never sprout at all.
NOTE: During my move, I had cut several rose branches and placed them in a grocery paper bag in my garage--only to have forgotten to bring them home for a week. The branches had been in a broiling hot enclosed garage without water, and needless to say, they looked pretty dried out to a crisp. But I didn't want to just toss them out yet (these were the climbing Charisma roses), so I got an empty plastic detergent tub and completely immersed the stems for 2 weeks (no changing water). Then I stuck them into soil and hoped for the best. Well, I got about a 50% survival rate.
When the rose hips are ripe, after about four months, cut them off the bush. Some rose hips will turn yellow, orange, or red, but others stay green even when they are ripe. You can open the hips as soon as harvested or you can store the unopened hips in the refrigerator for several weeks before opening. Then slice the rose hips in half, and open them with a knife. A butter knife will do just fine. Now, dig the rose seeds out of the rose hip with the knife, and throw away the pulp and outer shell.
Cover the cutting loosely, pot and all, with a plastic bag or plastic wrap and keep the soil moist. Putting a tall stake into the pot will hold the plastic away from the leaves. If the plastic touches the leaves, they remain wet and can succumb to a fungus disease. Along the same lines, make sure the condensation can escape from the plastic or the stem will rot.