Adjust oven racks to upper-middle and lower-middle position. Preheat oven to 400°. Peel and cut sweet potatoes into 1/4-in. julienne strips. Place in a greased 15x10x1-in. baking pan. Mix salt, cumin, thyme, cinnamon and pepper. Drizzle sweet potatoes with oil; sprinkle with spice mixture. Toss to coat.
Bake on bottom oven rack 25-30 minutes or until golden brown and tender, turning once. Meanwhile, in a large bowl, combine beef, onion and seasoned salt, mixing lightly but thoroughly. Press onto bottom of a greased 13x9-in. baking dish. Bake on top oven rack 15-20 minutes or until a thermometer reads 160°.
Drain fat from baking dish; place cheese slices evenly over meat. Bake 2-3 minutes longer or until cheese is melted. Cut into 12 patties. Place one patty on each roll bottom; arrange eight fries to form spider legs. Replace tops. Press two olive slices onto cheese to form eyes.