Did you notice any leaves getting black spots on them, turning yellow and then falling off?
Or it hasn't developed many leaves yet this season?

Are these older canes (like from last year) that have produced just a few leaves? If so, chances are the dormant buds were damaged during the winter and what you see is what you got. Modern roses bloom best on new wood. Bit the bullet and prune back to promote new growth with more leaves. I like the ingredients in Mills Magic Rose Mix for a fertilizer.

12-12-12 works just fine. I have more blooms than ever this spring. Blain's Farm and Fleet had a good price on 13-13-13 a few weeks ago. Also check Walmart and Meijer. Home Depot's 10-10-10 is too expensive. Get a big 30-40 lb sack.

First, check pH and add lime if needed.

For the main fertilizer, I like Mills Magic Mix; follow label directions on it. Also, add a tiny trace of gypsum, as roses need a small bit of sulfur.

Rose Tone is good--you can get it at your local Home Depot. If they don't have Rose Tone, try their Plant Tone. Lots of good stuff in them, including some alfafa.

Kate

Rose-tone for the long journey ahead, followed by Miracle Grow for roses for that needed boost into orbit.

I use Rose Tone, but I don't think your problems are a lack of fertilizer. Karl is probably right that you're seeing some winter damage and need to prune back to good wood. Is the rose in full sun? Lack of sun would also cause poor blooming.

The reason your blooms might not be opening up is because either you have thrips (insect inside the buds) or you still have cold temperatures at night. I use Rosetone also but I would use Mills magic Mix if I could find it locally.

Since I have over 90 roses and garden organically, I use alfalfa meal that comes in large bags from the feed store. I pour a cup or two over each rose, or less if they're babies, and then water it in thoroughly. I've had very good results, with healthy rose bushes and good bloom.

Ingrid

I never had a favorite fertilizer. My roses get soluble fertilizer exclusively now with the exception of Osmocote timed release in the spring after pruning. Osmocote will not kick in until the soil temp hits the high 60s, so it doesn't hurt to put it in early. I just go to Lowes and get five or so soluble fertilizers with varied analyses on them, and rotate them, with a different one every month. I apply a tablespoon to each big rose and a teasoon to each mini and let the irrigation carry it into the plant. The thing to keep in mind is that roses are heavy feeders and should be fed something (your choice) every month. Since roses can't read, they don't care what they get as long as they get.

I tend to go for organic fertilizers with about as much nitrogen as kalium, and just a bit of phosphorus. I also like compost and composted cowmanure. I really like seaweed both as meal and liquid form. The best seaweed has some nitrogen and lots of kalium, but not any phosphorus, so there has to be added a bit more nitrogen and phosphorus from something else.

I don't use only one type of fertilzier or any brand exclusively. I tend to go for the best offer, and with the idea that alternating different types might be good. I used to give my roses water soluble fertilizers of the Miracle Grow varity, but I ended up with more winter damage and fungus diseases than necessary. I even used a low-nitrogen firtilzer later in the season but it really didn't make much of a difference. So far I have had most luck with different organic fertilizers.

I have over 200 roses, and so feeding them can get a bit expensive. Especially because I have over 50 palm trees to feed as well...

Any opinions on what the most cost effective solution for roses would be ?