Bananas and coffee grounds are very mild fertilizers and so will not burn or otherwise hurt your plants, go ahead and use them whenever you want to. The coffee grounds are a mild nitrogen fertilizer, but I think you would want to use an additional fertilizer also, roses are heavy feeders, pigs about it even :-)

My personal preference is for alfalfa, meal or pellets, or made into a tea, about a cup (or gallon for tea) per bush every month, and I supplement with fish emulsion once a month, liquid seaweed foliar feeds, and compost and worm castings, scratched in around the bush, when I have them. Do a search on alfalfa, you'll find lots of posts.

Be careful about using bananas, unless you use organically grown. These days most of the bananas we get are extremely full of pesticides. Unless I buy organic, I no longer even compost them.

I don't use coffee grounds, but I have used banana peels on my roses for years with great success. They promote strong growth and strong stems, so even the biggest blooms don't nod their heads but stand up beautifully instead. I have tried using whole bananas but this seems to have the opposite effect, producing a lot of weak stems and flowers that flop over on weak necks. I grind up the banana peels with water in the blender and pour them around the roses twice a year, in spring and after the first blooming. About 2 peels will do it for a medium-size bush.

I also fertilize twice a year, with a mixture of Gardens Alive! organic rose food (great stuff), a little dried blood, ground up egg shells, kelp, a little epsom salts, and alfalfa pellets; then I mulch with compost or leaf mold. My roses flower beautifully but I still get blackspot (sigh).

If you wanted to make it as easy as possible you could probably get away with just the Gardens Alive rose food, plus banana peels for any bush with drooping blooms, or on which you want to encourage vigorous new growth.

Do you have to grind up the banannas? Could you just add them to the soil?

Ever got a banana peel stuck in your in-sink disposal? there's just about no way to grind a banana peel. Put them in the compost bin and let the worms do the grinding, you'll be a lot happier and so will the worms. And you'll get a nice high-nitrogen compost. Cheryl

Regarding black spot, it is the bane of rose growers. It is an airborne fungi that can also be spread by infected tools, clothing and insects. Free moisture on the leaves from rainfall, dew or excessive watering will favor the development of black spot. A control program begins in the fall with the gathering of and disposal of fallen leaves. Do not put them in compost but rather garbage. In the spring after the danger of frost is past, remove the old mulch and rake the ground thoroughly. I usually dispose of the old mulch. During this time I apply corn meal to the soil and let the ground lay bare to the sun's rays. After pruning the roses and removing any dead canes, as new shoots begin to appear, apply NEW mulch in generous amounts. These cultural pratices will go a long way toward controlling black spot. As leaves start to develope, I start a spray program that consists of 1 tsp. of baking soda and one half tsp. of a dish soap such as dial per gallon of water in a pump-up sprayer. I also fertilize monthly with a roses fertilizer supplied by a local organic nursery. It is applied to the soil and lightly tilled in. I really avoid foliar applications to prevent sun scald in our triple digit summer temps.If any one reading this lives in the Dallas/Ft. Worth area, I purchase this organic rose fertilizer at Redentas. Hope this is helpful in breaking the black spot cycle.