Build a cone-shaped mound of soil in the bottom of the planting hole, and test to see that the depth will be correct, with the bud union above or below the soil level, depending on your climate. Spread the roots out evenly over the cone, and fill in the hole, checking to make sure the planting depth is correct, and water well. Mulch the surrounding soil. Don't use fertilizer until you begin to see new growth. That way you will be sure that the plant has settled into its new site.
Roses have a reputation for proneness to pests and diseases.
For most rose ailments, prevention is the best cure. Fungus diseases such as blackspot, rust and powdery mildew can be controlled with regular treatments of fungicides. One is keeping your rose bed neat and free of fallen debris. Fungus spores overwinter in the debris on the surface of the soil, so removing it makes good sense. You can also remove infected leaves by hand as you notice them on walks through the garden.