Coffee grounds make a good fertilizer for roses, according to DoItYourself.com. Coffee grounds are considered organic fertilizer and environmentally responsible. They make the soil more acidic because of their nitrogen content, which is ideal for roses to grow.
Coffee grounds can fertilize roses in a variety of ways. They can be sprinkled around roses or added in to wood ash in a ratio of three parts coffee grounds to one part wood ash. Alternatively, 1/2 pound of coffee grounds can be mixed with 5 gallons of water and then sprayed on the plants. They can also be directly added to compost heaps to increase its nitrogen content.