well the title says it all.
if i cast 'ere we go on a orc unit that has a gobbo character in it,
does the gobbo get the re-roll to hit along with the unit?

the spell says it affects all orc units...

Why should he get a re-roll? To me there´s no argument for that and the rule is pretty clear. "All orc units ..."

More importantly do the Orcs get to re-roll?

Are they still an Orc unit, or are they considered an Orc and Goblin unit. Does this fit the requirements of the spell?

Vague spell is vague.

It's pretty clear to me, all Orcs get rerolls?

I was wrong about that. Page 100 - Special Rules second paragraph says the character counts as the same as the unit type he´s part of. So the goblin boss gets his rerolls.

- All orc units are affected
- Goblin char in orc unit counts as "orc unit"
- Spell affects all orc units
---> Goblin boss gets rerolls

Hmmm curious thing!

Thats cool.
But I still rage at this spell so much though for only affecting orcs. Massive annoyance, I want re-rolling trolls.

The spell targets Orc units, and then says that each unit gets to reroll.

So either

a) the entire unit including characters regardless of type gets to reroll (as per pg 97 and spells affecting a combined unit)

or

b) the unit is an ineligible target by not being an Orc unit by virtue it has goblins mixed in.

Stance b) is a bit tenuous as there is no rule that I can see that defines an 'Orc unit', there's one that defines a 'Goblin unit' on pg33 of the OnG Army Book but that is purely for Size Matters.

Orcs are stated as such on the paragraph above the goblin unit description.
The goblin unit rule seems to be there to cleary line out what is counted as a goblin unit. Who could argue, that an orc boy, black orc or savage orc is no orc and a "couple" of them are anything else than an orc unit?