the role playing part of the game would be the leveling up and stat juggling with different items ect. which is what an RPG game on the pc is defined as...

A role-playing game (RPG; often roleplaying game) is a game in which the participants assume the roles of fictional characters. Participants determine the actions of their characters based on their characterization,^[1] and the actions succeed or fail according to a formal system of rules and guidelines. Within the rules, players have the freedom to improvise; their choices shape the direction and outcome of the game.

"quote from wikipedia"

Roleplaying Ie LEVELING UP!!!! Buying new equipement to enhance your capabilities,etc...

You're being far to literal in how you're understanding the RPG or "Role Playing Game" tag on a game box. If a game has RPG elements, it's nearly always referring to the ability to level up and customize your character as you see fit, be it through items, skills, appearance or all of these together. It does not strictly refer to you assuming the direct role of a character and guiding him or her through a story or series of stories.

Its roleplaying in the same way Diablo was roleplaying. You are playing the ROLE of a DEMIGOD with certain abilities that you can develop.