Common diseases that affect roses in the UK are Black Spot (Diplocarpon rosae), Powdery Mildew, and Rust (Phragmidium tuberculatum).
A regular spray with a rose tonic such as Potassium Phosphite (Uncle Tom’s Rose Tonic) will help roses to keep healthy. Use alongside a proprietary feed during the growing season to keep your roses happy.
Don’t forget – whether you garden organically or not – roses need food and water and a good mulch of well-rotted manure in the spring.