> Inquire about why people would stand on a building. It's just not nice.

You're not so sure about that. Maybe they have permission to be there? Either way, it wouldn't hurt to check on them.

You introduce yourself and ask the people what they're doing.

One of them grabs a megaphone and answers you. They say they're Moxie and Molly, and they're working on repairing the building's roof.