Is it possible to set one rotation setting for one set of objects, and another setting for another set?
For example, if I’m building a plywood display box, I might care about the grain direction of the pieces that make up the skin of the box, but I don’t care at all about the grain direction of the ribs inside. If I want to cut them out of the same sheet of plywood, can the grain-sensitive pieces get rotations = 1 and the rest get, say, rotations = 4?
definitely possible 
I’m using OpenNest2, you just need to play around a little bit using two nestings in serie A and B:
in A you setup a nesting for your initial no-rotation curves (rotation = 1):
then the trick is to take the initial sheet polylines and subract from those the result of the nesting A, in such a way to create new sheets WITH HOLES ready to receive the nesting B:
copy nesting options and set rotations to 4 for nesting B:
nesting_multiple_rotations.gh (27.6 KB)
the only weird situation my mind is forecasting is if you would need -for instance in the above example- a third brand new sheet: in that case, because we have told opennest the sheets have a hole, I guess also the new one will have a hole 
for that reason, I think the B’s sheet component must always to be set to ONE COPY, and if you need to add empty sheets you always do that on A:
[edit] I confirm that thought, here’s an example with 4 sheets, where only the first two have holes:
nesting_multiple_rotations_2.gh (28.9 KB)
just a note, that is valid for rotations as well as any other Option
