The main reason is that your plants are new. They want, no, they NEED to grow roots to grow canes and leaves in order to support beautiful blooms. The whole NPK complex supports this growth, don't get all tied up in needing more P or K. There is usually too much of those two.

While I like MEF, I also prefer using some dry organic or organic-based fertilizer such as Espoma Rose-tone (or Holly-tone), Mills Magic Mix, Dr, Earth or whatever you can find locally. These help to condition the soil in addition to fertilizing.

How often are you applying the fertilizer?

diane nj is right. The first few years the bushes devote themselves to getting established. Having said that, a fertilizer with twice as much available nitrogen as phosphorous will stimulate the rose to produce lush dark green leaves at the expense of producing flowers.

Not a bad thing for a rose in its first year after planting, although it will frustrate you later as years go by.

I use Espoma's Garden-tone, but I also use it on everything else I fertilize and I don't have that many roses, either (just about six or seven).

Thanks for the replies. I've been fertilizing about every 4 weeks, about a gallon per bush.