If they have the salmon special that day (with little winter squash curls on top) order that. It is my all time favorite thing I've had at WDW. (And I have had a lot from fine dining establishments.)
Yes, they serve the Sally Lunn (sp.?) rolls at lunch. YUM! I haven't had the pot roast at 50's PT so I can't compare but have had it at the LTT and it was good, mashed potatoes awesome, and a VERY nice lunch break from the parks. I love the atmosphere there at Liberty Tree.