Well Avyn summed it pretty much up. I leveled a NM to 60+ and had much less skill points and tried to get a efficient skilling, so I used most of his recomondations that have been posted before.
One remark left:
For PvE, I found roots on higher level quite handicaped, since it becomes a longer range spell. I used it quite often as opening spell when soloing. This made me often do some steps afterwards to the target mob, since all other spells are with shorter distance. This makes you loose time.
So I downgraded roots to level 2 or so.