In a medium bowl, add oregano, rosemary, salt and pepper.  In a small bowl, whisk together 1/2 cup lemon juice and 1/4 cup oil.  Using a sharp knife, score the inside of the roast on a diagonal in 1-inch intervals.  Turn roast over; score fat cap.  Rub herb mixture over both sides of lamp; pour lemon-oil over roast.  Tie roast with butcher’s twine; place in large baking dish, cover with plastic wrap, and refrigerate overnight. 

Whisk remaining 1/2 cup lemon juice and 1/4 cup oil together; set aside.  Place roast on a roasting rack lightly coated with nonstick spray.  Roast at 325ºF until temperature reaches 130ºF, about 2-1/2 to 3 hours; baste every 30 minutes with lemon juice-oil mixture.  Remove from oven; tent loosely with aluminum foil.  Let rest for at least 20 minutes before slicing into 1/4-inch-thick pieces.  (Roast can also be cooled completely before slicing.) 

Prepare Tomato Jam and Shawarma Sauce while lamb roasts. 

For Tomato Jam:  In a large heavy-bottomed pot, heat oil over medium-high heat.  Add onions; cook until translucent, stirring often, about 3 minutes.  Add tomatoes, sugar, salt and cayenne; bring to a simmer, then reduce heat to medium-low.  Cook until mixture is thick and tomatoes are concentrated into a jam texture, 45 minutes to 1 hour, stirring often.  Remove from heat; set aside to cool to room temperature.  Transfer jam to an airtight container; refrigerate until serving.  (Can be refrigerated for up to 5 days.) 

For Shawarma Sauce:  In a large bowl, add yogurt, mayonnaise, lemon juice, garlic, oregano and salt; stir to combine.  Cover with plastic wrap; refrigerate until serving.  (Can be refrigerated for up to 5 days.) 

For Shawarma Seasoning:  In a large skillet, add cumin, coriander and fennel; toast over medium-high heat, stirring often, until the seeds start to crackle, are fragrant, and wisps of smoke rise from the pan, about 3 minutes.  Transfer spices to a large plate; cool.  In a spice grinder or coffee mill, grind spices into a fine powder.  Turn the mixture out into a medium bowl; stir in paprika, turmeric, curry, cayenne, allspice and salt.  

In a large bowl, add sliced lamb; toss with 6 tablespoons spice mixture to evenly coat.  (Store remaining spice blend in an airtight container in a cool, dry, dark place for up to 6 months.) 

In a large skillet, heat 2 tablespoons of oil over medium-high heat.  Add one-third of the seasoned lamb; cook until lamb is warmed through.  Transfer lamb to a large platter.  Repeat twice with remaining oil and lamb. 

Adjust oven racks to the upper-middle and lower-middle positions.  Place the pita bread on 2 rimmed baking sheets; place in oven and warm at 300ºF.  Remove from oven; spread Tomato Jam inside each pita, or if pita is very thin spread Tomato Jam on top.  Divide the lamb between the pitas; top with shredded letters and a few tablespoons of Shawarma Sauce.  Serve hot.

In a spice grinder or coffee mill, process fennel seeds until fine.  In a small bowl, add ground fennel, salt and pepper.  Add 2 tablespoons of oil; stir to combine.  Evenly rub lamb with fennel-oil mixture; roll lamb, tie and set aside. 

In a large heavy-bottomed oven-safe pot or Dutch oven, heat 1 tablespoon oil over medium-high heat.  Add roast; cook until browned on all sides, 10 to 15 minutes.  Transfer roast to a large plate.  Wipe out pot; add remaining 1 tablespoon of oil and heat over medium-high heat.  Add shallots, garlic, apples, carrots and celery; cook, stirring occasionally, until apples soften and mixture begins to brown, 8 to 10 minutes.  Return lamb to pot; add wine, broth, rosemary and bay leaves.  Increase heat to high; bring liquid to a boil.  Cover the pot and transfer to the oven.  Braise at 350ºF until a fork easily slides into the center and meat pulls apart with a fork, 3 to 3-1/2 hours, turning roast every 45 minutes.  

Remove pot from oven; transfer lamb to a large platter, cover and set aside.  Strain broth in the pot through a fine-mesh sieve.  Discard vegetables and herbs.  Wipe out pot; pour strained broth back in.  Bring broth to a boil; reduce heat to medium and simmer until liquid is reduced to 1-1/2 cups, about 1 hour.  Pour sauce into a fat separator; set aside to settle. 

Remove twine from roast and discard; pull the lamb.  Remove fat from sauce; pour sauce into serving dish and top with roast.  Drizzle some sauce over the lamb, serving the rest on the side.

Chef suggestion:  Serve with parsley gnocchi and a poached egg.