A rover travels for an extended period of time - weeks, months or even years - without ever settling permanently in one place. There is no specific destination.
A traveler can travel for a short or long period of time, but generally with some destination. A traveler could make short stops along the way.
A tripper is a person traveling for just a day or two for pleasure. Sometimes called a day-tripper. It is more common in England, I think, though my English friends can disagree.
There is one more definition of a tripper, originating in the U.S. A tripper can mean someone who has taken some mind-altering drug such as LSD or psilocybin (a drug from a type of mushroom). It was used more in the 60's and 70's, but not so much any more.