Hard to tell whats going on from the picture but...
Looks like too much mulch too close. Also looks like water could pool around the plant a opposed to draining away. There also seems to be foot impression around the soil, most likely not the cause but soil compaction can be an issue.
Roses like their water, but don't like being continuously wet, lightly damp or moist is OK. Location should also get plenty of sun.
From
https://www.fast-growing-trees.com/blog/double-knockout-rose-maintenance/
Double Knockout Roses thrive in areas that receive full to partial sunlight and prefer at least 6 to 8 hours of sunlight a day.
Make sure that your roses don’t sit in a low area of your yard that collects a lot of water runoff, or where standing water collects.
Double Knockout Roses will adapt to a variety of soils as long as it’s
well draining.
Double Knockout Roses prefer to keep their soil moist, but
not over saturated. Check on your soil every few days if it starts to feel dry then it’s time to give your roses a drink.
Don't go under the assumption all plants have the same cultural requirements (soil, water, sun..). Just because 1 type of plan is doing well doesn't necessarily mean all will. Sometimes even similar type of plants have different requirements.