Liquid inorganic fertilizers work great on rose bushes. I use one on mine every two weeks, or less frequently as long as it's looking good.
I had been having problems with my rose bushes losing leaves and not putting out blooms. I bought a powdered inorganic fertilizer that is made of bright blue crystals that you mix with water. I sprinkled them into a watering can and filled it with a gallon of water.
Then, I poured it over the leaves and blooms. I watered over the drip line, and I used half a gallon of the stuff per bush. The plant perked up within a day or two.
Sometimes, if we aren't getting a lot of rain or if it is scorching hot outside, the roses will need the fertilizer every two weeks. If we are having plenty of rain and temperatures that aren't quite so brutal, then one dose can sustain them for months.