My roses in the bed haven't been looking good for two weeks. The leaves are getting brown spots all over them and some are falling off. I water regularly, but despite that, more and more leaves keep getting affected. Could this be a fungus or is it due to the heat this summer?
This is very likely a fungal infection - either sooty mold or leaf spot disease rather than plain water shortage. The fact that you're watering regularly and it's still getting worse is a telltale sign of fungal disease. If it were just water stress, watering would help. The brown spots with their characteristic appearance (often with a dark border) and leaf drop are classic symptoms. Heat and dryness can encourage the fungus, but they're not the root cause.
Here's what you can do now: Remove all affected leaves generously - including the ones on the ground - and throw them in the trash, not the compost. Make sure your roses get air circulation from below and aren't standing too close together. Water in the morning directly at the roots, not from above onto the foliage. That reduces the leaf moisture the fungus needs to thrive.
If it doesn't improve, a fungicide will help - there are also organic options based on sulfur or copper at the garden center. The sooner you treat it, the better. Next year, water preventatively and consistently clear away fallen leaves in autumn, and you shouldn't have such a bad outbreak again.
Don't just keep watering the way you have been - with a fungal infection, you'll only make it worse because wet leaves feed the fungus. If the affected leaves don't fall off on their own, I'd remove them and dispose of them (not in the compost), then water your roses from the base so the leaves stay dry.
When exactly do you water - more in the morning or in the evening? That matters, because fungi really take off on wet leaves overnight, while watering in the morning gives the leaves time to dry out. If you're watering in the evening, try switching it up and see if it improves.
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