Crikey, not at all well?! Only time I've seen something like this, with what appears to be multiple problems unevenly spread across a plant was with a soft fruit bush. I planted a small bush which wasn't obviously potbound but it gradually started failing. I dug it up & the roots were actually looped in a tight knot! Once teased out, replanted, pruned & fed it recovered fairly quickly.
Rose experts may spot what's wrong but I'd suggest lifting it out & looking at the roots as a start. Any pests, squishy roots, etc. can then be treated. If they're okay then you can put it back, no harm done...

To my point of view, roses don't do well in pots. They seem to get stressed and suffer from lack of water, nutrients are quickly washed away and become more susceptible to pests and diseases. I would transfer it to the garden.