The ash is the result of burning ivy and rose cuttings and I would like to know if I should dig it back into the soil around the roses?
Yes, but lightly, and if the leaves were not diseased. You also can add it to your compost pile if you have one. Here is more:
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/using-wood-ashes.htm
Caterpillar eating roses leaves
roses leaves have a sticky wet look what can I do
You have a bugs problem. I would suggest spraying the foliage down with a good insecticide twice, ten days apart. That should take care of the situation.
Can I grow roses and azelas together?
Typically no, it is not a good idea. Roses do not like having to compete with other plants for their nutrition and water. I would suggest creating a rose bed and then a separate garden area on either side of the rose bed, at least 4 feet apart, and plant azaleas in those other gardens. The two azalea planting areas will frame and highlight the rose bed.
The existing bed has had the same variety (simplicity) for over 25 years which is at the base of a grassy knoll. The grass is sprinkled in summer months. The roses have their own drip system. The roses last about 2-4 years and then have to be replaced. Should I consider changing the soil or adding ammendments ( what kind). What should the character of the soil be like when I plant the bare root plants and should I fertilize them when I plant them?
This article should help:
https://www.gardeningknowhow.com/ornamental/flowers/roses/bare-root-roses.htm
Most of my potted plants (roses, azalea, helebore) were covered in granular feed when it was mistaken for decorative covering. After a few weeks, I realised & removed it all but my plants are now brown twigs. I tried to prune as it's spring in a hope they will recover but they're all "dead". Do I give it time or is it a lost cause?
Did you also flush the pots with water repeatedly? If not, do that. You might even replace the soil. I still see some green so they might recover.
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/what-is-fertilizer-burn.htm
When is the best time to prune roses
Here is a link to an article I wrote on this very topic. For the major pruning I am an early spring pruner (Late April to Early May here in Northern Colorado.) Link: https://www.gardeningknowhow.com/ornamental/flowers/roses/pruning-roses.htm