Of course it will depend on what the soil in your area is like but most soil is not perfect. There are four important parts to a good rose soil inorganic materials, organic materials, water and air. The best soil is often called loam. Some things you can do to create a good soil are as follows:
Be sure to dig and aerate the soil every growing season.
Add some organic material such as compost to the soil.
Ensure that the soil for your roses is dry and crumbles easily before you begin to make improvements. If the soil is to wet it will stick together. It should not be to dry either.
Ensure there is good drainage in the soil. Water placed in a hole in the soil should drain within 15 minutes or so.
If you do not want to take the time to prepare the soil yourself you can buy high grade potting soil at most gardening stores. It can be quite expensive depending on the size of your rose bed but it will ensure the proper mixture of organic and inorganic elements.