There is really not much difference in elevation between US 287 or I-25 to Laramie. The US 287 is about 20 miles shorter. If you are an Interstate type person, stay on I-25.
You can use this website to see elevation on your route. Just click to add start and finish points, then grab the line to add way points.
How far did I run? - Create running maps with On The Go Map
You will get a really nice quick descent going into Pendleton, Oregan but I don't see any way to avoid that one.
Funny thing is, I am sitting in Kennewick right now getting ready to head farther west.