When you plant you can embed bottomless plastic bottles -or plantpots by the plant. I have done this with my strawbs and courgettes, which are also in a well that the water can run into. You could also drape soaker hose around (or a pierced pipe) which I do in my greenhouse -only there's been no rain, so the waterbutt's empty, so the soaker hose won't soak :(
When watering you can direct the water at the base of the plant and not onto the foliage -probably easier if you take the rose off (or use a jet nozzle), but you risk washing the soil away from the base of the plant.
The guttering idea sounds plausible, for things in rows, it wouldn't matter if it slopped over the sides either.
Jeremy