Some experts on these forums say that foliar food doesn't work. I used to use Miracle Grow in a sprayer. I can't say that I can tell any difference since I quit doing it. One of my favorite old rose experts I used to see every year was Vernon Rickard, who owned Almost Heaven Roses in NC. He used Neptune's Harvest as a foliar spray. He was very experienced and knowledgable and he thought it worked. Experts used to say that margarine was better for you than butter. Then they said trans fat was worse than butter.

So experts do change their minds. It probably wouldn't hurt if you gave it a try. I will check out Cropmax but guess it's unavailable here..still maybe there's something similar. I do believe that leaves absorb things, especially the underside of leaves. Various rose chemicals that are sprayed on leaves are said to be systemic..they get in through the leaves and are IN the leaves. So I don't know why food wouldn't be the same. Roots may be the best way for a plant to absorb nutrients but it might not be the only way.

Other people will tell you that water is the main thing roses need in order to absorb the nutrients that are naturally available in soil. Could be your rose acquaintance has plenty of water in her garden.