Just the other day, when DCA did not have EMH we arrived about 10 minutes before rope drop - we went on Soarin first thing then we went and had a leasurely breakfast at Flo's. So by the time we made our way to RSR it would have been likely close to an hour past opening and we walked on to the ride by using single rider (my DH and my DS actually rode together, beside each other even). The standby line was only 40 minutes at this point so I can't imagine it would have been awful had we headed straight there at rope drop.
Now, this was on a Thursday when crowds were lower than normal so it does depend on when you are going.