Remove tortillas from refrigerator. Let stand at room temperature while preparing filling. Combine cream cheese, onions and olives. Spread a thin layer of cheese mixture in each tortilla. Arrange four ham slices over cheese. Tightly roll up each tortilla, wrap individual rolls in plastic wrap. Refrigerate for 3 hours or overnight. To serve, cut into 3/4" diagonal slices.
For crab wraps: Omit black olives and ham. Add 1/4 cup chopped red pepper, 1 cup shredded cheddar cheese and 1 can crab meat (or 5 oz) chopped imitation crab to cream cheese mixture. Continue as directed above.