Q:

What is killing my rose and what is the antidote?

Below is what the dead leaves look like
The still alive ones are all green and those grey spots on them

A:

Black spot is a common fungal problem on roses almost everywhere that roses will grow, they are very susceptible to it. In the UK, we spray fortnightly with something like Roseclear Ultra, which contains a systemic fungicide, from leaf break until leaf fall in an attempt to keep it at bay. Without such a regime, roses generally succumb, unless you've been clever enough to pick black spot resistant varieties (Kordes bred ones are the most disease resistant).
Clear up fallen leaves as soon as you notice them,and clear away all leaf debris before winter to clear away overwintering spores. Find a fungicide product in your area that will treat this infection. Other things that help are correct pruning to promote maximum air flow around the branches, no under planting other than with ground hugging plants,planting in full sun, feeding with a specialist rose food as often as recommended, and mulching with composted manure. These last two recommendations are simply to help the plant have more strength to resist by providing optimum nutrition.
You mentioned your Hostas having 'perforated' leaves. Hostas are a favoured target for slugs and snails, so if you don't use slug repellent/killer products from early in the growing season regularly, holes in the leaves are inevitable.

