You can add many natural fertilizers to promote healthy soil for your rose plants. These include: Banana peels are a source of magnesium, calcium, and potassium. Epsom salts. 3 to 4-day old animal manure. Never use new manure as this can burn your plants. Bone meal rich in phosphorus. Dry blood meal rich in nitrogen. Greensand rich in potassium. Seaweed rich in nitrogen. Rock phosphate-rich in calcium. You can add some of these on their own while others can be mixed together for better results. However, it is essential to carefully determine what your plants lack and replenish the soil with those nutrients. Ensure you do not add too many nutrients, as excess will bring more harm than good. Your foliage may turn unhealthy and yellow.