Let me try it another way. Look at Spirit of the Century for a second. Characters in SotC are defined by their aspects- generally one word or short phrase descriptors that define the character - so "tough as nails", "big and dumb", "loudmouth", "strange luck", or "poor as dirt", could all be aspects. When a character's aspect causes some sort of in game complication, the character is awarded Fate points. Pretty much similar to Action points in many other games.
So, let's look at a possible situation. I have a character with the aspect, "poor as dirt". During play, the party steals a honking big diamond and needs to fence it. They give it to my character to hold because the guy they stole the diamond from has never seen me and won't suspect that I have it. Play begins with the party returning from meeting a fence:
Player 1 - So, Hussar, where's the diamond? We're gonna be rich!
Hussar - Well, here's the thing. See, I was outside in the alleyway feeding a stray dog, when the diamond slipped out of my pocket and the dog snatched it up and ate it. It ran away.
Player 1 - WHAT!
GM - Ok, Hussar, that's worth a Fate point. Nice.
Player 2 - Well, what did the dog look like and which way did it run off?
Hussar - ((extemporizing)) Well, it was a black dog. Kinda big. It had a white patch on its chest.
Player 2 - ((To the GM)) Can we track this dog somehow? Let's look in the alleyway.
Player 3 - ((Looks at his character sheet and sees "Loudmouth")) *Very loudly* You mean to tell me, and correct me if I'm wrong, that a large dog has run off with our very expensive, very hard to get diamond? Is that what you are trying to tell me?!?!
GM - ((Grins)) Several of the patrons of the bar hit the exit at speed. Player 3, here's a Fate point for you.
Now, the entire scenario - find the dog before the locals do, while trying not to run into the people who they stole the diamond from in the first place - is entirely generated by the players. The GM is running with it because it's fun for everyone. Yet, the GM had no hand whatsoever in this plot line. Every decision that was made was based in mechanics in the system and not from what would be in the character's or group's best interests.
To me, this is 100% role playing. If it's not roleplaying, then, to be honest, I have no interest in roleplaying whatsoever. If the only way I can roleplay is to passively consume whatever plot the GM/DM decides to create this week, then bugger that for a game of soldiers. I have no interest. I want to be able to effect changes in the campaign.
And, as a GM, I want my players to be so into the campaign that I can sit back and let them do all my work for me.
So, did I roleplay or not? Did my editorial control over the campaign somehow impede my ability to roleplay?