Traditionally the best time to plant your rose is between autumn to early spring when the plant is dormant, if you can’t plant your rose straight away you can leave it outside in its container and water the compost whenever it feels dry.
Before planting its ideal to dig the area in which you will plant your rose before hand and mix in lots of compost and organic matter.
Also make sure that your rose is well watered by watering it in the container at least 1 -2 hours before planting.
Dig out a hole big enough to hold the roots comfortably, the ideal level for planting is with the graft union (where the roots meet the stem) at ground level. This is normally the depth its been planted in its pot, however not always. You must ensure that the graft is above the soil otherwise this could cause suckers from the rootstock to grow.
Tip the rose gently out of its container, loosen the soil just enough to expose some of its roots, right before planting sprinkle some rootgrow directly onto the roots and around the sides of the hole.
Place the rose into the hole, check its at the right height and correct position, if your not sure, a handy tip is to place the fork/spade handle or a bamboo cane across the hole giving you a level to match the compost on the rose against, planting just below this level, hold the rose with one hand and gently back fill the soil around it, firming it down as you go. Make sure the soil around the roots is firm enough to ensure no air pockets but not packed down solid.
Lastly give it a good water.