You can access your Steam key by going to www.humblebundle.com/store/keyresender and entering the email address you used to back Road Redemption(or your paypal email if that is how you backed Road Redemption).
You will then receive an email containing all of the Road Redemption related keys associated with your email address, including your Road Redemption steam key page.
I know I'm a little late to the party, but I didn't see a Steam key when I had humble re-send all of my keys. I was a backer via PayPal, as I was in the Alpha when it first launched, however, my old PC died and I was looking to re-download the game. Any pointers?
Well when you go to your account page and see the library tab and then look for road redemption in your purchases tab and it is not there then yeah you need to probably shoot an email to darkseas since they don't always catch stuff on this forum. firstname.lastname@example.org