All roses are greedy feeders and like a lot of fertilzer. It should be given when the leaves start to break out and after the first flush of flowers is over. You can use boxed rose fertilzer and use according to package instructions.
Roses also benefit from a monthly foliar feeding.
Organic fertilzers can be applied in early spring and allowed to break down over the season. Those gardeners with sandy soil may have to apply fertilizer more often because of their fast draining soil. No nitrogen should be applied six weeks before the first frost as it encourages growth which will be killed.