Have you dosed your roses with Epsom salts yet? It's rumored to be very good for the plants. Matter of fact, a few years ago an elderly lady in Iowa spoke highly of using Epsom salts on her tomatoes, also.
Hogwash! Epsom salts is magnesium sulfate, a source of both magnesium and sulfur, both essential nutrients for plants. But your plants would benefit from a dose of Epsom salts only if your soil is deficient in either magnesium or sulfur.
Even though sulfur is not naturally abundant in soils, forget about needing to feed it to your plants. Plants get it incidentally with other fertilizers, from composts and manures, and from acid rain.
Magnesium occurs naturally in soil minerals, often in sufficient quantity to meet the needs of plants. Admittedly, some soils start out with insufficient magnesium, or have had their magnesium washed out by rain. Plants are most likely to be hungry for magnesium in acidic, sandy soils where rainfall is abundant. Sometimes alkaline soils or soils developed from peat bogs also can be magnesium-hungry.