The brown and yellow spots on the foliage of your hosta look like Anthracnose, a fungal infection encouraged by wet and warm weather. I do not think your new roof is to blame, but the plants look crowded, and overcrowding encourages the fungus among us. I think you should uproot the bed of the hosta and improve the soil with compost or leaf mould. This will help make the plants more disease-resistant. Then, you can remove any infected leaves from the old hosta you uprooted and replant, giving at least one foot apart from each plant so that there is plenty of air circulation. Do not use overhead watering on the hosta as this also encourages disease. If you replant only the most healthy plants with the least amount of leaf damage, you may be able to start fresh. Dispose of the other hosta plants with infected leaves. Keep growing, Marianne Binetti