I called Alaska Air customer service this morning.
After I have my record locator, I go to the Alaska site and pick my seats. If available, I am okay to pay the upgrade to the Premium class seats.

That was exactly what I was looking to find out. I can book the flight for 12,500 miles for saver seats instead of 20,000 for anytime seats ( I am trying to make the flight form ROC - PDX with only one stop. I can than pay to move up to a Premium class seat - that works out perfect for me in my situation.

Thank you