Hi, welcome to GoY, some time go, gardeners were always told that the graft union should be below ground level, [mainly because it looked a bit unsightly], more recently, keeping the union just above ground level is recommended, this way you can tell instantly whether a shoot is of the required rose, or a shoot from the root stock, because it will be below the union if it's from the root stock, and above the union if it's the rose you want, Derek.