The Byrds' 5D was my first truly rock album. You've probably backtracked through their early work, but if not, may I recommend their 3rd-6th albums in order as a starter (Fifth Dimension, Younger than Yesterday, Notorious Byrd Brothers, Sweetheart of the Rodeo). From there you can go further backwards or forwards as you feel called. But 3-6 in my opinion is their canon.