The common rose diseases are black spot, rust and powdery mildew, and it definitely isn't any of those. It COULD be some kind of nutritional deficiency (eg chlorosis) but that usually shows up as even patterns along the veins. Given the speckly pattern, I'm with @Dovefromabove that something has been sprayed on!
Posts
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
It is possible, i assumed it was a specific disease