2) Make a mound. Once you have a suitable hole, place a cone-shaped mound of soil in the center of the rose whose dimensions roughly match the cone defined by the roots. (If it is a potted plant, don't do this step.)
3) Place the rose into the hole. Try to make sure the roots are straight and evenly distributed around the hole. If it is a potted rose, check to make sure the roots aren't encircling the rose.
4) Ammend poor soil. If you live where the soil is very high in peat, pure sand and gravel, or limestone, consider digging out a hole about three feet in diameter and two feet deep and planting the rose in that hole. Use imported 'rose soil' in the hole. Most people, however, can add things to improve the soil. Gypsum will loosen heavy clays; so will compost. Lime will help neutralize acid soils. Sandy soils can be made usable by adding lots of good compost. Sometimes mixing twenty or thirty percent good potting soil in with native soil can give roses a good start.
In ammending soil keep in mind that where there are abrupt changes in soil composition, most plants will not send new roots across the boundary, so if the soil in a hole is markedly different than the surrounding soil, create a zone in which the two are evenly mixed to help the roots make a transition into the surrounding soil.
5) Fill halfway with earth. Add some slow-release organic fertilizer - perhaps a few tablespoons, and fill the hole with water. When the water has drained from the hole, fill in the hole with soil.
6) Pack the soil firmly. If your soil is so full of clay that this seems like you are just making bricks, then you probably should have added some compost to your soil.
7) Shape the surface. I like to make a cone-shaped indentation that catches water and sends it to the rose at the center of the hole. This is convenient for watering later on. If you water with a hose, and the rose is planted on a slope, some kind of dishing around the rose is imperative; otherwise all the water runs away from the rose.
8) Mulch. Place about 3 inches of mulch on the hole. This will limit evaporation, keep the soil cool, provide some organic matter to fuel life below ground, and limit weed growth.
9) Water. Apply plenty of water to the rose. Water not only is required to cause the roots to become active, but it also aids in settling the soil into the hole, helping to fill large voids. This is essential to improve soil contact with roots. Water daily through the first August, weekly thereafter.
You might buy your roses from a store, or you might order them through the mail or on the web. Big box stores are sometimes decent places to get the most popular hybrid tea roses, floribundas, and shrub roses. Many serious rosaphiles purchase roses from mail order nurseries or on-line.
Roses will arrive either as dormant bare root plants or as actively growing plants. Most of the rules for planting are the same; but the timing for the two are different. If you order dormant, bare root plants, you will want to plant them about six to eight weeks before your last average frost date. Some advocate planting them as soon as you can work the soil in spring. Often, your supplier can estimate this well when you order.
If you are receiving roses in pots of one size or another, you will want to plant them about a week after your average last frost date. Bear in mind that these roses have been growing vigorously in a greenhouse, and sometimes a whiff of frost in the air will kill them cold.
Bare root roses arrive in boxes with bits of peat to keep them moist. It is best to soak each bare root rose in a barrel of water for 4-24 hours befors planting. In both cases, keep the plants between 40F and 55F, in shade, and adequately moist.
Most of the business of planting the rose lies in digging the hole. Farmers long ago coined the phrase "Dig a $10 hole for a $5 tree." Skimping on hole size can impare the development of a rose. This is especially true if the soil needs to be ammended.
So here are the steps in planting a rose:
1) Dig a hole. A rule of thumb that I use for most roses is to dig a hole whose diameter about matches the diameter of the plant at the end of two years. I may give small roses a hole not much more than 18 inches across. Shrub roses get holes about three feet across. Climbers planted along a wall may get holes a little bigger than this. In any case, the holes should fully accommodate the roots.
If the native soil is not too poor, then there is not much reason to dig a very deep hole; about one shovel's depth is good enough. Dig deeper, and the rose will sag too far below the surface after being planted.
If the soil is poor, and is being replaced with imported soil, then digging down eighteen inches or two feet may not be a bad idea, just be sure that the improved soil at the bottom of the hole is packed tightly so that the rose does not sink in when watered in.