Posted: 29/07/2016 at 10:39
From the look of it your soil is clay. The best thing you can do to improve the soil is to dig in as much well rotted manure as you can. I'd add a large bag of grit for every 3 ft as well. I'd actually lift those roses in early winter, prune them back hard, dig in your compost and grit, then replant them. Then after replanting I'd add another layer of well rotted manure to decompose over the winter months. You may need to continually add further layers of manure over several years to get the loam you're after. Good roses need good feeding. Manure and a proprietary rose feed every year produce the best roses.