The general purpose Osmocote Plus Outdoor & Indoor is great fertilizer for roses. Roses are hungry beasts so you can use the recommended amount of Osmocote at one capful or 3 tablespoons for every four feet of garden space which is about one rose plant in most gardens. Sprinkle the granules around the roots then work them into the top 1 to 3 inches of soil. You can also use liquid plant foods on your roses in the spring or at the same time you apply the Osmocote. Again, this double dosing of plant food is because roses are heavy feeders and the liquid plant food is available almost immediately to the roses while the slow release Osmocote is available gradually as the soil heats up and the plants grow faster in the late spring and summer.