Product Owners and Product Managers - When Is It Our Job to Do This?

When is it our job to do this, and when is it that of a product owner or product manager? This is really tough. Since I am not a UX designer, I spent very little time within the design world. Reactive research are things like, we've created something and it's not working. Can you do research to understand what is going wrong? Another reactive research project might be, hey, we're creating a prototype based on, I don't know, gut assumption,. Somebody's dream that they had, a thought and a shower, can you test it?