Firstly, choose the right variety to grow for your situation, so do your homework. If you want to grow a rose on a patio a dwarf variety such as Sweet Dreams is not only the perfect size but also very attractive. Climbing roses need particular care when choosing. Mme. Alfred Carriere is a wonderfully fragrant and attractive choice to grow over a tree but far too vigorous for a back garden trellis.
Many popular varieties should be sold by garden centres with a health warning as they are so prone to disease. Possibly the best example is Rose ‘Zephrine Drouhin’, undoubtedly a wonderfully fragrant variety and thornless, but so prone to mildew. Grow it at your peril. New roses are only marketed if they are proved to be resistant to disease and able to be grown successfully with a minimum of spraying.
Once you have your rose plant them generously. Plenty of organic matter, a handful of good rose fertiliser, and plant with the bud union just below ground level. Then a good watering, once a week for the first season. A happy rose! If, as is very likely, rose diseases appear, the modern systemic fungicides are very effective and 3 applications should do the job.