Remove any weeds in the area you will be growing the roses. This is a step that is necessary regardless of the type soil you have but absolutely crucial to the healthy development of your rose garden.
Add a thick layer of organic compost to the clay soil. Organic compost can only benefit the rose plant, so the more you are able to put down, the better.
Aerate the compost with a small, hand-held shovel. Aeration is the process of making small holes in the ground in order to expose more of the soil to air. It also makes it easier for water to penetrate the soil and the compost.
Plant rose seeds in the soil by completely covering the seeds with soil and compost. If you are transplanting a fully grown rose bush, dig a hole deep enough to cover the entire root system of the plant.
Water the soil with a slow stream of water from a hose or with a watering pot. Clay soil has the tendency to become muddy if it is watered to quickly. Watering slowly and using a watering pot will give you more control over the flow of water.
Add earthworms to the soil after the seeds have been planted. Earthworms help fertilize the soil with their droppings.