The role of Software Architect is typically not well defined in most organizations and I've found Gregor Hohpe's description of The Architect Elevator to be the most enlightening.
I discovered Gregor Hohpe's book 37 Things One Architect Knows About IT Transformation: A Chief Architect's Journey on a long business trip a few years ago when I was trying to understand what it means to be a Software Architect. I've always had a sense that it was more than just a really really senior developer. Gregor's model of an Architect is someone who rides the organization elevator and leads change has provided me considerable perspective at how a Software Architect can bring value to an organization.
This video provides a good introduction to what Gregor's description of an Architect. I especially like his diagram at the end.