There was an interesting article in Harvard Business Review last fall about star and guardian tasks. Star tasks are those that are more strategic while guardian tasks are more operational. The article discussed how effective pirate ships were at dividing these tasks, since one person is typically not good at performing both kinds of tasks.
The world of project management is the same. The star tasks would be having a vision for the product or seeing the big picture. These are tasks often associated with the product owner or sponsor. The guardian tasks would include planning out the work, getting the right resources, or managing the budget; obviously more in line with the project manager.
So just like the pirate ship, with a captain to handle the star tasks and a quartermaster to handle the guardian tasks; you should keep these to roles separate on your project. And as the project manager, if you have a team member out of line, you can make them walk the plank.