Are you going to replace the roses with new ones? In which case you should definitely replace the compost. If the roses are still alive, just replace the top 2 inches and give them fresh compost to top them back up. Also, mix in some rose food.

I have just done exactly what VT suggests. I used a granular rose fertiliser forked into the new topping of compost. they look happier already. I did actually repot one completely but only because it needed a larger pot.

I would replace the compost every three to four years anyway - they are hungry plants. A good mix is half loam and half general purpose compost, but always ensure they get enough food - greedy brutes!