How you travel with your rats really depends on the type of transportation you are using-- car, train, plane, etc. Drives of a few hours aren't much of a problem. A few grapes, and or other food with a high water content will keep them from getting thirsty (water bowls and bottles should be removed). Anything that can fall should also be removed from their cage for the journey.

If you're traveling by plane or train, you'll have to make sure you're allowed to take rats with you before you board. This link provides a list of airlines that will let you fly with your rat(s):
<http://www.interlog.com/~audiotre/ratair.htm>

Here is a good article on making very long car trips comfortable for rats: <http://www.rmca.org/Articles/moving.htm>