This is one of those theories that really push it.
The idea that Professor Romanovskaya is posing is that it is theoretically possible for a sufficiently advanced civilization to essentially commandeer one of these objects and use them to get off the planet. While the many rogue planets (insofar as they have been observed to any significant degree) are barren and essentially huge wandering asteroids incapable of sustaining human life, Professor Romanovskaya goes on to theorize that some may contain surface and subsurface oceans. Along with a sustainable atmosphere and a dependable gravitational force, this could make this a useful resource for interstellar travel.
For more, check out this Giant Freakin Robot story.