Feeding Roses

I am in the middle of pruning my roses in large pots and now about to feed them as buds are well established. I normally use Bayer plant food but sometime also add farmyard manure on top. Is there any need for the manure as I also have cobbles on the soil which I take off first to use the rose feed. Therefore they are not required as a mulch. Can you overfeed roses? Thank you in advance.