Most of the leaves look very healthy. I would imagine that the few yellowing leaves are the result of the early frosts.

Looks like it may be a fungal disease. a close up of a couple of leaves would help. Spraying with a product like Roseclear will help.

see if this link helps.

https://www.rhs.org.uk/Advice/Profile?PID=776

Thanks Jimmytheone and Seaburngirl. I'm not convinced it's frost damage as the yellowing has appeared more recenty than the last frost. I'm due a visit to a garden centre next week, so I'll get some Roseclear when I'm there. The photo doesn't show the yellowing very well - it's a more definite yellow than in the picture. I've taken a closeup, but don't know how to add it in a reply, so I'll start another thread.

It could be over-watering. There are many reasons that can cause rose leaves to yellow.