History:
[Threeboot Legion never explored many of the characters backgrounds but based on a couple of comments Cos makes and what we see of his family it seems reasonable to say his backstory is similar to previous versions of the character which is what I'm using here.]
Born to an average, low-income Braalian family, Rokk Krinn displayed considerable skill in the sport magnoball in his youth leading to him being scouted for a professional team. He quickly became one of Braal’s top athletes, supporting his family with his earnings and eventually giving him the opportunity to leave his homeworld for the first time on a tour of demonstration matches to other United Planets worlds. While he was travelling he ran into two other youths - Garth Ranzz who possessed unusual electrical abilities and Imra Ardeen a telepath - while defending some local underagers who were being unfairly persecuted by the law. The incident made Rokk aware of just how unfairly underagers were treated by the United Planets, a situation he couldn't just ignore. He left the magnoball circuit to join Garth and Imra in what started as a way to show the oppressed youth that they could stand up for their own rights and eventually became the Legion of Superheroes.
The Legion quickly grew into a major political force, garnering support from teens across the galaxy and attracting many powerful individuals. Rokk, as leader of the group, found himself with the increasingly difficult job of balancing the Legion’s own goals with the concerns of the UP who sought to control the group. The situation was made more difficult by the looming threat of interplanetary war, fuelled by the actions of a man known as Lemnos. The UP ignored the Legion’s warnings regarding the threat Lemnos presented leaving them to stop him alone. After they succeeded in preventing the conflict, they grew massively in popularity and were offered funding as an officially sanctioned, independent branch of the UP, an offer the temporary leader Garth accepted, much to Rokk’s dismay on his return.
The Legion’s next major challenge occurred when the Earth was invaded by an alien race known as the Dominators. The Earth fell before anyone had a chance to fight back but Cos devised a plan to force the invaders back to their own homeworld, devastating their infrastructure and ensuring the Dominators would not be a threat for some time. However the Dominators had a back-up plan that would come into affect years down the track and could lead to the destruction of the entire UP. Leaving them alone to rebuild and come back later was not an option. All the same, the rest of the Legion was horrified to learn that Cos had commanded that a bomb, capable of destroying the entire planet, be built. Worse, he ordered that one of his own, potentially fatally ill teammates, Mon-El, deliver the bomb on a suicide run. The plan succeeded and the entire planet along with all it’s inhabitants and a member of the Legion were apparently obliterated. In truth the bomb had trapped the Dominators and Mon-El in an alternate dimension where the Dominators would be unable to carry out their back-up plan and Mon-El would be safe until a cure could be devised. Cos chose not to reveal this to the rest of the Legion, ostensibly to prevent Mekt, a dangerously unstable individual they had temporarily allied with, from releasing the Dominators or worse in a bid to free Mon-El.
It was at this point, facing impending charges of genocide from the UP that Cos was approached by a group calling themselves the Knights Tempus who claimed they were from the 41st century and had come back in time specifically to recruit him as part of their team. He agreed to accompany them and disappeared without so much as a word to his team, his friends or his family.
Character Background and Personality: As leader of the Legion of Superheroes, Rokk is a prime example of the concept of being married to the job. His strong will and natural tendency to take charge make him a good choice to lead the team and he takes his job seriously. It may be said that he takes it a little too seriously as he dedicates himself entirely to the team and it's goals, rarely taking time to himself to relax or visit his family. He sees himself as responsible for the future of his entire generation and it's taken him some time to accept that others may be able to carry that burden too rather than him taking it all upon himself.
He expects equal dedication from those that he works with and doesn’t take any perceived betrayal well. For the most part Rokk is calm and level-headed but when he does snap he has a hot temper and is not above getting in fights with his own teammates. While he is not unsociable, Rokk tends to be somewhat distant from those around him. He’s more used to playing the diplomat than honestly befriending people and it takes a while for him to become close to anyone. Even his closest friends he tends to keep at arms distance and is unlikely to confide in them. But he still cares about those around him and wants what’s best for everyone even if he can’t always accept that he may not always be right about what that is.
At his heart Cos is an idealist who passionately believes that a single person can change the world for the better. This idealism is tempered by his practical nature as he knows that ideas can’t achieve anything without action. He pursues his goals with a single-minded determination and is not above using underhanded measures to achieve them, though he has a strict moral code he adheres to and will not ask anyone to do something he is not prepared to do himself. He’s not above taking the easy way out though and has more than once manipulated events to avoid making a difficult decision himself.
Sexual Orientation: Canonically Cos only ever shows interest in one person which is later shown to be the result of power mess ups and which he gets over completely once he realises this - to the point of having her essentially poisoned for her own good. It seems unlikely he has ever had any serious romantic relationships or any prior sexual encounters. It seems likely he’s uncertain regarding his own sexuality and, as the 31st century is generally implied to be more open regarding sexuality, would not be put off by the prospect of a relationship with a male so long as they got along. In the end Cos is a romantic who wants to fall in love more than he wants to have sex and so the sex of his partner is of little concern compared to their compatibility.