It very-much depends on the terms and conditions of the cruise ticket contract you agreed-to. I noted that the cruise reservation information with respect to the name of the passenger was verified against proof of identity at check-in, so it seems clear that if there was to be any change in passenger, it would have had to have been agreed-to by the cruise line in advance.
How far off is the cruise, how many days is the cruise and what cruise line? You just can't sell it to someone. Up to a certain point you may make one name change (for a fee) but not two. Depending on the sailing date you may be able to get a partial refund.
I haven't encountered any insurances that would actually allow you to sell the tickets yourself. Depending on how far out the cruise is, you may be able to get a partial refund. You may also be able to change one of the names like Cruise Guy suggests. If it's not too painful, consider going by yourself or with a friend and having a great time.
That is one of the best aspects of cruise insurance through RCI directly, as they'll refund 75% of your cruise fare, no questions asked, up until a certain time before your cruise. It seems well-designed to serve the precisely need that Justin had.