While in line for RSR two weeks ago, I heard a couple ask a CM the very same thing and they were told they'd have to wait in line again. Someone can correct me if I'm wrong but that's what I heard. The couple was disappointed and heard one parent say to the other that only one would ride. - MonteKristal  308.7 #566 9:22AM

They do have parent swap. We did it on Saturday. Just ask a Cast Member and they will give you the pass. You wait in the Fast Pass line with the Parent Swap ticket. It is good for 2 people - 1313mm  14.6 #5723 9:27AM

"Rider switch"- usually you get the paper from the CM. one parent goes on with the older child while the other one waits with the baby or smaller child. On completion of the ride the parent waiting with the smaller child switches with the other parent and goes on the ride with the older child. You take the fast pass line to go back on the ride, not the regular line up. - calidream1  379.4 #354 9:28AM

Disney's own website says RSR does rider swap. - Coaster  9128.8 #1 9:29AM

They do have it but the CM told us it would be faster to go in the single rider line twice. Ask the CM. It depends on the crowds. - 2princesses  82.8 #3240 9:46AM

Thank you everyone for the quick responses :) - Keala76  293.1 #655 10:26AM