Huh?
The "Full English" breakfast on the CCR menu (posted in recent days on the relevant thread) includes "rosti potato".
The "Full Breakfast" on the current TATL to LHR F menu includes "potato rosti."
I'm pretty sure they're on the breakfast buffet at the Arrivals lounge -- those previously frozen triangles of shredded potatoes (which Americans would call a "hash brown" and may or may not be considered a rosti by the Swiss).