Beyond the normal considerations of "how deep to plant" and "what fertilizer to use" your rose planting's first decision is location, location, location because without this important step your efforts may be in vain. Rose gardens depend on your choice of sunlight; at least six hours - and I mean direct sunlight for optimum results
Next let's consider the soil - roses are hungry eaters and need nutritious soil. To grow roses that are winners, they do not like too much clay or too much sand. Try clumping a handfull of your soil to see if it holds the mold and does not crumble easily.... a sign of too much clay. If the soil crumbles too easily and does not hold the mold, it has too much sand. God's soil should hold the mold in your hand but crumble easily. The soil should also not be too acidic, i.e., contain too much limestone or too much chalk.
Further, there are trees and other plants that will extract water and nutirents from the soil. The tree roots that extend far beyond drip line will be in competition with your plants - therefore try to plant your rose garden as far away as possible and avoid this risk. Lots of roots where you are digging indicate a possible problem for growing roses. There are some climbing roses and some rose shrubs that are the exception, but generally speaking, they prefer to be mixed with other roses or non-invasive plants.
With the perfect location for your rose planting, now is the time to consider the basics such as how deep the hole should be. A good measure is slightly larger than the size of the pot the plant is in or root system of the plant. The depth of the hole depends on the climate that you live in. Colder areas need to be slightly deeper - when in doubt, talk to other neighbors who grow roses as to which depth is the right one. Depths may be different for lots of reasons but everyone can benefit from loosening the soil at the bottom of the hole.
You can also place some compost in the bottom of the hole plus a sprinkle of bone meal which is a source of Phosphorous and is slow acting but encourages healthy root growth. Spread out the roots slightly after you place the rose plant into the hole. Refill and make sure the soil settles around the roots. Water the roots before you cover them with the last couple of inches of soil. Firm the soil slightly and water the plant at this final step.
Ahhh, the perfect rose planting has been accomplished - give yourself a pat on the back.