Hello jamesmorrone!
The Brienzer Rothorn is covered by the Regional-Pass Bernese Oberland, not by the Jungfrau Railways Pass. You can best download the validity maps from the pages I linked to in order to see where the passes are valid.
All you need to know about traveling by train, bus or car in Switzerland.
Hand picked Swiss hotels and other accommodations are right here.
Swiss Travel Pass promotion 25% discountOnly if purchased in July 2021. Free cancellation.Buy via the SBB travel centre at https://shop.switzerlandtravelcentre.com or HappyRail at https://www.happyrail.com/swiss-travel-pass.
