Which type of rotation do you mean? Camera panning rotation? Personally I don't even want to use middle mouse button, because mine's hard to press. But being able to personally customise these bindings should definitely be something for a controls update part 2 patch. (Early in the new year, I'd hope.)
How about block rotations on mouse wheel scrolling? That would need a keyboard modifier, though, to save in interfering with zoom. The natural choice for that would normally be [Alt], I guess, but that currently hides the block you're placing from inventory, heh.