You know, I really don't mind the hills since I have a shower at work. These rides are my only cardio exercise and 16-20 miles a day has helped me lose some weight over the last six months.
I leave between 6:30 and 7:00 most days. I'm an administrative law judge w/ the Oregon Office of Administrative Hearings and my schedule is as regular as clockwork: M-F, 8:00-5:00. I'm inclined to take a break on nice mornings at the wildlife refuge that connects Cook Park in Tigard with the MUP bridge over the Tualatin River. Five minutes to sip some coffee and watch the birds is a nice way to start the day. I sometimes work at home on Tuesday and Thursday afternoons. That occurs more frequently in the winter when its dark out for both the morning and evening commute.
I do occasionally take the Roy Rogers route. It's a bit longer (10.5 miles versus 8.5) but is 5-10 minutes faster and considerably easier if I don't push it. I don't mind doing the Fanno Creek route. I've done it a couple of times but find the Cook Park route too pleasant to give up, despite the hills. Variety is nice though.