by role playing do you mean playing along the story line?
if yes you should DEFENETLY change to GW because the story line is so much more dynamic
now how it works:
you meet all the players in a town. you can join a party taht is doin a quest or a mision. if you go out of the town you have a personal map, meaning no other players that are not in your party (which you joined in the town)
there is 3 types quests.
Primary quests: you need to complete those quests to go ahead to a mission town and to advance in the story line
mission towns: its a town that is fully dedicated to a mission. you can repeat that mission as much as you want even after you are done. the missions are the main story line. normally every mission leads you to a new towns (there is only 3 missions in the whole game that are exception)
secondary quests: you dont have to complete those quests to be able to advance. but they give you experience and skills that help you level up
you have alot of skills on every class you play, but you cant equip more then 8 at a time, and you can change your build only in a town, so that means that you have to think in advance and make sure your build has damage output, self defence, self heal. since you cannot have more then 8 people in 1 party your party has to also plan a "party build", which makes RP of GW a strategy that requires team work and planning.
as for PVP, there is an "arena", which has 2 3 or 4 teams in it. a team cannot hold more then 8 or 6 people, so again, the party has to develop a strategy before heading out (example: ok so we have a elemental which is base damage dealer, Ranger which is gonna support by interrupting ennemy's spells, 2 wariors to take first waves of damage, 2 monks to heal the party etc)
the leveling up doesnt take long at all (comparing to WOW) since highest level you can get to is 20, and its only after you get to level 20 that the real fun and challenge begin. you done HAVE to spend alot of gold on armors or weapons, because the low cost ones do the same functions, but look way diffrent the the more expensive equipment.
have fun