Well, strictly speaking what to do exactly depends on what nutrients are in the mix you used and what your irrigation water has in it. Most home gardeners don't get that technical and just follow one size fits all recommendations made by nursery clerks and other home gardeners--for better or worse. Did the mix you use have fertilizer in it already? If not expect to be fertilizing perhaps several times per year. Sometimes in commercial production of container nursery stock in soilless podding media both dry and liquid fertilizer regimes are used.

Hi, Bboy: Here is what I used for the rose bush, Uncle Malcolms Lifeline by Whitney Farms:

In addition to the rose food, both Whitney Farms and Dr. Earth are now producing "designer" potting soils which incorporate many of the ingredients I used to add to my planting mix. Uncle Malcolm's Potting Soil by Whitney Farms contains softwood bark and sawdust, peat moss, perlite, pumice, animal manures, bat guano and kelp meal. Garden Bloom Rose Planting Mix, by the company that produces Dr. Earth products, contains fir bark, forest humus, peat moss, perlite, worm castings, chicken manure (highest of all manures in nitrogen content), alfalfa meal, bat guano, bone meal, oyster shell and dolomite limes. Again, it may be more expensive in terms of dollars, but it saves money in terms of time. I have no fertilizer in my home system. Does this product contain enough fertilizer or should I add some now or in April?
Thanks for responding!

Should say on the bag how long they expect the fertilizer component to last (based on the assumption that everyone has the same conditions, of course).

I'd recommend against fertilizing your rose until it's been in the ground for a year. If you're planting with amendments in the hole, the rose should spend its first year developing the root system, not the canes and leaves. Lots of folks add epsom salts to the planting hole (as I do). And I'd avoid a planting mix with chicken manure which might burn tender roots. Whitney Farms is a great product if you're buying ready-made. Next year you can fertilize in the spring with a handful of epsom salts and a good shovelful of aged manure or rose food. Many rose growers will feed once monthly after that first feeding.

The Gardener & Bloom potting soil is great stuff but you'll still need to add fertilizer through the growing season. Roses should not be fertilized til they have about 4" of new growth in spring. the alfalfa meal will be a good nitrogen source but for organic fertilizers to work you need to have active microbes in the potting soil to break the stuff down. that means, don't use insecticides on the potting soil. You can supplement with fish emulsion, worm tea or pretty much any nitrogen source throughout the growing season. Nutrients wash away fast in pots because you have to water so often. But so long as you have nice healthy vigorous growth you've got enough fertilizer already.

I would not recommend adding Epsom salt to the planting hole, whether in the ground or in a pot. Epsom salt is very water soluble and will wash right out. A little bit goes a very long ways so you can add a sprinkle once or twice through the growing season.

Chicken manure is the best thing readily available. Roses love it. I hear rabbit, alpaca and llama manures are better, and non burning, but they're not that easy to come by as the chicken manure. I've never burned anything myself with chicken manure, and the G & B stuff is very good for any heavy feeder, not just roses.

While it's still so cool out, adding more fertilizer will not make spring come any faster. I normally don't start feeding my roses til April, and they won't bloom before June, just because it's not warm enough til then. A potted rose you could speed up by putting it up against a south facing wall in a sheltered spot. Black nursery pots especially warm up fast and get the rose growing sooner.