To qualify for copyright protection, the property would have to be [b]an original work of authorship fixed in a tangible medium of expression[/b]. That means, something slightly more original than a phone book but that is also fixed; which means for example: on tape, in a book/manuscript, photograph, or even on a computer hard drive or memory. A catch phrase, simply uttered aloud is not capable of copyright protection. Even had the phrase been part of a work fixed in a tangible medium, it likely fails the originality test. Many people have used the phrase and it likely would be considered to be in the public domain. The phrase could be used as part of a larger work that in of itself is capable of protection but even then such a short part of that work, already of dubious originality, would not be capable of protection itself.
Here's an interesting twist though. If a recording device had picked up her husband saying "Let's Roll", then the owner of that tape would be afforded copyright protection for the content on THAT tape. Not the words themselves, but the content captured on the tape. In other words, that person would have the ability to use, make, sell, license etc. the tape and its contents for his own purposes to the exclusion of others! That's cool.
As a phrase, it could come to be so associated with a [i]product or service[/i] that it is capable of signaling its origin, but that protection would fall under common law trademark rights or under the general unfair competition provisions of the Lanham Act (Federal Trademark Law). Since this is just a catchy phrase not used to signal the origin of a product or service, no dice here either.
This is just another example of the general public not really understanding protection of intellectual property rights and spouting off about protecting something that cannot be protected.
Edited to wire my non-spelling head together with my ass.