I don't play my necro much, but I think the answer is mostly no.

What you want is called Spell Haste at lower levels; I can't keep up
with all the variations at higher levels (Haste of Solusek, etc.).
One of the quirks of Spell Haste is that the spell must have a minimum
casting time for it to take effect; otherwise the spell is already too
fast to get hasted.  For example, Spell Haste IV will reduce casting
time of spells by 15%.  The limitations are a maximum spell level of
65 (with diminishing returns over the next 10 spell levels) and a
minimum casting time of 3.0 seconds.  That is, a 3.0 speed spell gets
hasted to 2.6 seconds (fractions rounded up), but a 2.5 speed spell
gets no adjustment at all.

I scanned the spell list quickly, and most of a necro's root spells
cast faster than 3.0 seconds.  Your best bet seems to be Greater
Immobilize at 1.75 seconds casting time, with the added bonus of a -30
resist adjustment for your target.  There is a loophole with Spell
Haste the allows one exception.  The minimum casting time decreases to
2.0 for Spell Haste II and 1.0 for Spell Haste I.  The level 34 Root
can be affect by Spell Haste II and has a casting time of 2.0,
potentially giving a hasted cast time of 1.7 seconds.  Given the
choice between a 1.7 cast and a 1.75 cast with a resist penalty, I
think Greater Immobilize is still your best bet.

Unless someone else knows something I don't?

- Prelgor