There are several things to consider when looking for a site to plant new roses.
Roses need a minimum of six hours of sun per day to grow well and produce their flowers. Consider planting roses in a south-facing exposure for maximum sunlight. An east-facing exposure is also good as it will receive morning sun. Morning sun will hasten the drying of dew from the plants and be cooler and less stressful than afternoon sun.
Good air circulation is also important. Many of the disease problems common to roses are more likely to occur when the plants stay wet for extended periods of time. A site with good air circulation will keep plant surfaces drier and reduce the incidence of disease. Avoid planting roses too close to one another, to other plants or to buildings or to other structure.
Roses must have soil that drains well or they will do poorly. You may need to amend the soil with organic matter or even consider raised beds, if the drainage in your yard is not sufficient. Roses will grow best if the soil is on the slightly acid side--pH 5.5-6.5.
When planting roses, soil preparation and size of planting holes are both important.
Whenever possible, enrich the soil with organic matter. This will improve drainage and make the soil more fertile. It will be most beneficial if you can prepare a planting bed rather than just amending the planting hole itself. This encourages the root system of the plant to spread out into the prepared soil, and develop more fully.
After the planting area has been amended with organic matter, it is time to dig holes for the individual rose plants. The hole should be both deep and wide enough to accommodate the root system.
If you are planting a bare-root rose, you will have to build a soil mount to support the plant as bare-root plants come with no soil of their own. The mound supports the plant and allows you to spread the roots out in a natural pattern. Special care must be taken with bare-root roses. The roots should be soaked in water overnight, prior to planting, to insure that the roots are fully hydrated.
The canes and roots may also need to be pruned. Try to maintain three-to-five canes per plant and prune them to three-to-five buds per cane. Prune the roots so that they are a little longer than the length of the canes.
When placing the plant in the planting hole, be aware of how deep the plant is set. In harsh climates, roses that are grafted should have their graft union one-to-two inches below the soil line to prevent winter kill of that graft union. Roses that are growing on their own roots can be planted at the same level at which they were planted in the nursery.
Once the rose is planted, be sure to water it thoroughly. "Transplants often have limited root systems and need regular watering to insure that they become established in a timely fashion.