As a rule of thumb, roses will need 2 - 3 ft. If necessary, an elevated planting bed should be considered. And organic materials should be chosen suitable to the soil conditions in the landscape. Not only do they represent potential nitrogen, but they help retain soil moisture as well. A quality soil test performed before the incorporation of organic materials will assist in determining which materials to add.
Occasional fertilization is a deliberately vague term.
Depending on the fertilization method, access to the rose may be necessary anywhere from twice a month to twice a year. In the drawing, the front rose has the best accessibility for supplemental fertilization. Regardless of the fertilization method chosen, overfertilization should be avoided. The rose can metabolize only so many nutrients, depending on water availability, root development, soil temperature and type of nutrient. Excess nutrients can leach into subsoil water tables or run off into streams and lakes, causing hypereutrophication and subsequent pollution.