Roberto was Sam's co-leader in X-Force #20-28Sunspot has such potential to be a great leader, but too many writers had him act like a potentially evil, spoiled hedonist, or waste the character in a sidekick role. The only time he tends to lead is when he's evil or misguided.
Roberto was Dani's co-leader in Young X-Men #1-12
Also I would call Roberto's time as Black King of the Hellfire Club as neither evil nor misguided. He kept the HFC mostly subdued and from perpetrating much evil for a long sustained period of X-Men history. But I guess proactive prevention isn't as flashy as fisticuffs with the HFC so he doesn't get credited.