Rose is pretty much like any woodland plant. It makes a really hard-coated seed that does best by never being dried. Clean your seeds out of the hip ones its color changes away from being green. Take still-damp seed and put it in with some barely damp peat moss in a ziplock bag, put your seed into the fridge (not the freezer). Plant them as you would any other wintersown seed (see winter sowing forum).
Eventually spring will come, seed will germinate. You can tease them out of their milk-jug or tote when they have at least their second set of true leaves. Its still going to very tiny.
Grow it in pots or cells till it gets big enough. Often at least a year.
Rose' percentage of germination can be all over the map. Irrespective of your skill at germinating them. My fix is, more is more. I put a half a cup of seed into a jug. Most years I will get more than 100 to germinate. I put two seedlings per cell.
If you are breeding, you're going to have to select for your traits, and propagate or graft the ones that make your grade. Give away or sell the culls.
I don't breed rose. Its just easier to grow rosa rugosa from seed. The hardscrabble gardeners that want my rose usually want them for hips, for food, or herbal uses.
