Where I work, the same people do everything when it comes to development; we just put on different hats. When we change those hats, we really change. We are hardly at our desks, because we are usually in one of the design rooms with lots and lots of white boards. Sometimes these sessions last 1/2 a day, sometimes everyday for a week or two. Once we think we have a plan and its documented and then approved. We change are hats, everyone takes their piece and its off to the races.
Our company has architects and data architects. The architects just give us guidance on an overall picture for the structure of the company. They tie all of the branches together and try to keep everyone from doing things their own way. I.e. common means of persistence, five layer architecture, the big picture stuff.
The data architect is actually in our design sessions helping us, and doing research on existing data resources.
I plan on getting the architect certification, because I believe it will help me as a developer with my designs, not because I want to oversee the big picture of the system.