Found a fare BUF-LAS on UA, fare basis LA14AN.
4 transfer limit, no min stay, routing on Expedia looks pretty wide-open.

Example itin:
Outgoing BUF-ORD-LAS leave Feb 8 7:40p arrive Feb 8 11:56p
Return LAS-DEN-ORD-PHL-BUF leave Feb 9 7:29a arrive Feb 9 9:46p

4702 miles assuming 500 mile min/segment, cost $135.30

Haven't played around with it too much so there might be other availability/better routing. Not a UA person but I saw this fare and figured I'd share.

Also, this is my first time posting a fare so if there's anything that I forgot to add my apologies.