In large glass baking dish, mix together mojo, garlic, sazón, cumin and cinnamon stick. Add lamb to marinade, using hands, rub marinade into lamb; turn to coat completely. Cover lamb; refrigerate at least 4 and up to 24 hrs, flipping once. Heat oven to 425°F. Remove lamb from marinade; reserve ½ cup marinade. Using paper towels, pat lamb dry. Season with adobo.
Heat oil in large roasting pan over medium-high heat. Add lamb fat-side down. Cook until golden brown, flipping once, about 8 minutes. Add reserved marinade and 1½ cups water to pan. Transfer pan to oven. Cook, basting every 30 minutes, until internal temperature registers 140°F for medium rare, about 1½ hrs., adding water in ¼ cup increments if pan becomes dry.
Transfer lamb to cutting board to rest 10 minutes; tent with foil to keep warm.
Place roasting pan on stove over medium-high heat. Add 1 cup water to pan. Using wooden spoon, stir and scrape bottom f pan to loosen browned bits. Bring to a boil; season with adobo, if needed. Transfer sauce to gravy boat. To serve, spoon sauce over sliced lamb.
The citrus juice in GOYA® Mojo Criollo contains citric acid which breaks down tough proteins in lamb. To ensure that the marinade penetrates to the bone: Using the tip of a paring knife, make numerous ¼ inch-deep incisions on the flesh side of the leg. Pour on the marinade. Rub it onto the surface and into the slits, then flip. Let sit at least 4 hours to allow the juice to do its work.