Copyright law is the wrong place to look for the answer, because the production company or studio would usually own the copyright to the original work and have the right to make derivative works based upon it. But, that wouldn't be the end of the story.
There is a separate common law tort for "commercial appropriation of a person's name or likeness" which is usually considered to be one of the privacy torts even though it looks more like an IP right in one's own image in practice. See Restatement of Law (Second) Torts § 652C. This states:
652C Appropriation of Name or Likeness
One who appropriates to his own use or benefit the name or likeness of
another is subject to liability to the other for invasion of his
privacy.
Comments:
a. The interest protected by the rule stated in this Section is the
interest of the individual in the exclusive use of his own identity,
in so far as it is represented by his name or likeness, and in so far
as the use may be of benefit to him or to others. Although the
protection of his personal feelings against mental distress is an
important factor leading to a recognition of the rule, the right
created by it is in the nature of a property right, for the exercise
of which an exclusive license may be given to a third person, which
will entitle the licensee to maintain an action to protect it.
b. How invaded. The common form of invasion of privacy under the
rule here stated is the appropriation and use of the plaintiff's name
or likeness to advertise the defendant's business or product, or for
some similar commercial purpose. Apart from statute, however, the rule
stated is not limited to commercial appropriation. It applies also
when the defendant makes use of the plaintiff's name or likeness for
his own purposes and benefit, even though the use is not a commercial
one, and even though the benefit sought to be obtained is not a
pecuniary one. Statutes in some states have, however, limited the
liability to commercial uses of the name or likeness.
A broad overview can be found in lecture slides here. The modern trend is that the right survives death, but there is a split of authority over that question. There is also an equivalent to fair use protection under the First Amendment, but that wouldn't be applicable in the kind of case discussed in the question.
The case that created it involve some who was used as a model in a prominent logo or advertisement for a product sold in stores (IIRC it was oatmeal), who did not consent and was not paid for being the model. The Court held that there was a common law right to compensatory damages for the profits unjustly obtained without consent from the commercial appropriation of the individual's image.
Of course, you are correct that Carrie Fischer almost certainly contented to and was paid well for use of her image in Rouge One. But, actor contracts with a movie production company regarding this kind of use would vary greatly and one of the reasons that Disney probably compensated her and obtained her consent rather than taking a hard line with her and trying to use her image without her consent based upon past contracts, is that they would have believed that they would need her willing cooperation as a major supporting character in two more movies.
The harder case is one where rather than using a manipulated image from a prior movie via CGI, they instead use an exact clip from a prior movie that was consented to and paid for, in a future movie. This too, however, would turn on interpretation of the contact between the actor and the production company, against the backdrop of the commercial appropriation tort claim.
Not every country and not every U.S. jurisdiction has adopted §652C or the equivalent as part of their law. But, it is the law in all of the U.S. states that are central to the movie making business. Usually, an express choice of law provision in the contract between the actor and the production company would choose one of those U.S. states (usually California or New York) as the one governing the contract between the parties.
