Why not raise the bed further? You have decent drainage already in place.

I planted "White Diamond" rose from Heirloom 3 years a go on top of a huge rock. There was a valled in the middle of the rock so I filled it up with new soil and of course plenty of fertilizer and every year the rose prospers more and more. Not to mention that I get nice white roses. I also add new soil on top of the old soil in the spring and late fall.
Hope that helps in some way.
Carolina

I wish I could raise the bed but it is just a narrow triangular strip along the side of the driveway which drops off on a steep slope on the opposite side. I think by the time I had it built up there wouldn't be much space left for the roses. I would also be a bit concerned with car or structure damage as that triangle is where the drivway narrows to the road.

Like "White Diamond" I have tried to have most of the roses in there of the smaller variety, at least no climbers. So I guess we will just have to see how they do. I hope they don't drain too quickly as they will have to be hand watered.

I have a friend of mine who uses rock instead of mulch and has been for years to the point to where there is a good layer, like you describe of small rock. She planted 3 Knock Out roses last spring in the one bed by digging deep and filling with good soil. I was over there on Sunday and all three look great.