Overfeeding roses??

You'd have to try pretty hard to over roses. But there's different needs for roses in containers than those that are in the ground. Those in the ground can get a better root run and have a better ability to search for moisture and food. I have a Kings Ransom rose [knocking to 30 years old] which is in sandy soil which was a choice of my wife's when we were just getting into gardening. It has never been spectacular in blooming or growth now matter how heavy I have fed it, either general, potash or phospate specific fertilisers. I have looked up it preferences and of course the word is that Kings Ransom doesn't like sandy soil, so we were fighting a losing battle there!! I have 3 difference climbing roses in poor soil by my pond where I can't use fertiliser because it might enter the water. They're happy to be left alone except for the annual trim. In the borders I have Uncle Walter, Crazy for You, Regensburg, Trumpeter, all in enriched, over the years, soil in the borders,Oh!, and a Masquerade climber on a south facing wall. They're all in different positions, good, very good and poor soils and they've all different in feeding requirement. | don't foliage feed as I like to get the liquid feed around the roots where it's benefit is more immediate but that's all down to preference. Container grown roses rely more on the gardener for their nutrient supply and the root run is more restricted reducing it's ability to absorb them. So long as you don't feed them with too much nitrogen I don't think you can really over-feed roses.