Some rose diseases and pests are just annoying. Aphids for example, or blackspot. They can be controlled, and while they might cause some distress to the plants, they aren’t going to kill it. Mosaic on the other hand is a totally different kettle of fish. It affects a variety of plants, not just roses.
Rose Mosaic is a virus, and it is incurable. The thing about this that I really hate, is the possibility that it can pass from plant to plant via pollen. As a hobbyist that enjoys rose breeding, you can imagine the havoc an infected plant could cause.
This is all about getting certified “virus free” roses. Mosaic almost always affects grafted roses, so as someone that prefers to grow older style species or own rooted antiques, I have been lucky with avoiding this (so far, fingers crossed!).
If you get any of your new roses from cuttings (as I do) then there is always a slight risk you have taken them from an infected plant that wasn’t showing any symptoms at the time.
My advice with this… once you are sure you have a case of Rose Mosaic, don’t bother with pruning away the affected portions of the plant. You are only masking the disease, and it will grow back. Instead, be totally ruthless… dig out and either burn or bin the plant. Never ever take cuttings from an infected plant.
It seems that not all rose nurseries take enough care to use uninfected stock. In the US, if a rose was grafted onto Dr Huey, then there is a chance it carries the Mosaic virus, even if it appears symptom free.