I think we may be on to something here regarding this Roadblock......
The large round disk like things may very well be maps showing the location of where each leg took place, i.e., Amsterdam, Florence, Italy, Burkina-Faso, etc.It was also pointed out that there is a U-turn and cluebox under one of those large round maps and of course we see Christina standing at a U-Turn as well.
My guess is that the person doing the Roadblock must go to each large round map and perhaps somewhere on the wall or on a piece of paper put down the order of tasks performed on that leg. Further they if there was a speed bump or U-Turn or FF they would also have to indicate if it was used/performed. There may be more to it but I think we have a majory memory task here.
For instance in Leg 8 in Mumbai, India
Speed Bump: Kynt & Vixen
Detour: Paste 'Em and Thread 'Em.
U-Turn: used by Kynt & Vixen on Nick & Don
Roadblock: Deliver propane gas canisters
Only after they put each leg in the correct order will they get the final clue to run to the final mat.
so that picture of the Christina doesn't mean there is an actual U-turn but rather she is trying to recall the order of tasks on a previous leg.