There seems to be a double issue here: how the technique is performed and how the ukemi is executed. In the interests of clarity, the following is how I understand the vertical component and the horizontal component of the technique.
When the technique is done omote, the kaiten (rotation) is on a vertical plane between uke's head and arm, which is held vertically. Whether the ukemi is a roll or a breakfall depends entirely on how low the technique is executed, whether tori is at the side of uke or slightly behind, i.e., how 'tight' the taisabaki is, whether tori holds the head or neck and for how long, i.e., whether during the technique tori lets go early on and allows uke to roll in a preferred direction, or holds on to the head and forces a breakfall.
When the technique is done ura, the kaiten is on a horizontal plane and involves uke's head and arm (which is spun round on to a horizontal plane like a spiral). Again, the ukemi depends on the height of the technique and the 'tightness' of the taisabaki leading to the throw. I myself prefer a particular type of 'spiral' taisabaki, but the ukemi from this can be difficult.
Here we teach kaiten-nage to beginners and thay have no particular trouble with ukemi from the omote form. For ura, we make sure that both tori and uke know exactly where uke will be thrown. For ura, at least in the form that I do the technique, this is quite difficult to master.