Well cared-for roses need regular feeding and attention. Just the fact that roses are normally pruned each year means that the nutrients are removed permanently from the area. (The pruned sections of the rose are basically the nutrients that were in the soil.)
Most shrubs in the garden are left to find their own way in life and are not normally subjected to the pruning regime of roses, therefore the loss of nutrients to the soil is lessened.
One of the most successful and environmentally friendly way of feeding roses is by the use of organic mulches applied each year. However, action within the soil has to take place before the organic material can be broken down into readily available food for the rose bush. Sometimes, this micro activity can even rob the soil and rose of much needed food during the decaying process.
A well balanced fertilizer applied at the time of pruning is normally a good way of feeding roses. If the fertilizer used is an organic type - such as bonemeal or fish Blood and Bone, then this should be applied a few weeks prior to pruning, for this type of feed takes a little longer to work.
There are many brand names of rose fertilizer available for feeding roses, but any good well balanced feed will do the trick at this time. Later in the growing season, then a fertilizer slightly higher in phosphate will be better for this will provide the right type of nutrient for flower quality.
If roses are not fed properly, then tell tale signs of diseases and general disorders will show up in the bush and flowers later on in the season.
Feeding of roses is not a complex matter, once you realise that the main thing is to replace all the lost nutrients and to help the rose regenerate all of that new growth that is required to support the hungry flowers!
Whilst the soil does a marvellous job of supporting plant life - if left to its own devices - it will need a little help and support itself when asked to continually support the growth of a hungry child!
I tend to use an Osmocote-type (slow release fertilizer) with a 16-8-12 analysis. This is applied at the start of the rose's growing season when the higher Nitrogen (N) ratio is good for new stem growth - needed after pruning. The Potash and Phosphate (P and K) ratios are enough to help the flowers and root system to develop well as they spring into growth later in the season. The beauty of this type of slow release feeding is that a single application in spring, will be enough to feed the rose throughout the growing season, as the nutrients are released according to moisture and temperature ratios. The damper and warmer the climate, the more feed is released. This neatly coincides with the growth pattern of the rose bush.
There are liquid feeds and also foliar feeds available for rose feeding. The latter simply feeds the rose bush and does little to replenish lost food reserves in the soil. Both liquid feeds and foliar feeds will need to be applied quite often throughout the growing season.
Basically, if you expect your rose to recover from an annual pruning session, then you will have to lend a hand in feeding it.