Robin saw the cloaked figure leap up onto the roof just before he did. So he and Bruce weren't the only costumed vigilantes running around. That was either a very good thing, or a very very bad thing. For one, he knew how Batman was about sharing his rooftop space. For two, you never knew who was good and who was bad; sometimes it was too late.
Well, time to take a chance. It wasn't like he couldn't take a hit; he very much could. And metahuman? Possible. But as far as he was concerned, he had a current outlook of "bring it on". It could never be said that he wasn't at least slightly self-destructive, especially lately. And his cage had sure as hell been rattled.
Which...wasn't to say he went up there looking for a fight. He thought about actually just tailing her for awhile, following, seeing what was going on. But he was itching for some answers, and if she couldn't give him any, maybe she'd be decent company for a little while. Maybe.
He worked his way onto the rooftop, letting his boots hit the ground with an audible noise, but saying nothing. He was enough in the light that he'd be visible, but not entirely. No point in playing entirely clean, after all; it wasn't his style. Not anymore.
((Actually, he can't *resist* being several stories up. Hope that's okay!))