As you probably already know, cooking them, boiling for at least 20-30 minutes reduces the lectins in them to a negligible amount, and it is important to do that.
I don't know if you can roast them instead....but I wouldn't because I don't know if that would serve to reduce the lectins.
Kidney beans are the most dangerous to not cook enough.....
and chickpeas, I know you can soak them and then make falafels and roast them without boiling them. So black beans are a mystery to me.
If you just soak them, they aren't going to be soft enough to eat....so I'd boil them first.