Exactly, it's right there in the name. It's both role-playing and a game, both parts are important. Rules create a common understanding of how the world functions and how your actions are going to affect it. Everyone at the table knows, to some extent, what you'd be rolling to try something, how good you'd be at that roll, how difficult it appears to be, and the likely consequence of success or failure, allowing the same kind of informed decisions sitting at a table in front of a character sheet and a pile of dice that you'd be able to make if you were your character living in the game's world. None of this inhibits role-playing, it enhances it.