21-year old Colombian forward Valencia has signed with the Timbers permanently after last season's loan from Independiente Santa Fe whilst 28-year old defender Miller joins after ending his time with Swedish club Halmstads BK.
Valencia, who spent last season in rehab from a knee injury, has enormous potential according to Timbers general manager Gavin Wilkinson.
"As a club it is imperative that we take a young player with tremendous potential and help him develop into a proven player in MLS," Wilkinson said in a statement.
"The hope and belief is that he can deliver on his potential and fight for a starting position in 2013 and continue to grow into a star in this league. While his injury led to a disappointing season for Jose last year, he showed great resolve, and we are looking forward to his continued progress."
"Ryan is an experienced pro and a great addition to the club," Timbers coach Caleb Porter said in a statement.
"His ability to go box to box as a right back fits what we are looking for in that position. He is another proven piece that brings traits we want in the locker room as well."