The resurrection of every single person that lived (and is not in gehenna) will be during the 1000 year reign of christ. They get a second chance. That's why jws can be happy for all the catastrophies, terror attacks etc when people die today, as they would get a second chance whereas they wouldn't if they died in armaggeddon.
Only after the final test when satan will be let loose again, mankind will live in perfection.
They quote Revelation 20, Romans (The verse that everyone who dies is aquitted of his sin not respecting the context), Acts.
The way they spin it to come to these conclusions you can read in the "Keep in god's love" book.
One could ask:
If any person who ever lived on that planet is returning, wouldn't there be not enough space and resources for all to live?
The standard answer you will hear. Actually there are not so many who walked the earth. And Jehovah will make a miracle.