Heat oil in a skillet over medium-high heat. Cook beef and onion for 8 minutes, breaking beef into small crumbles, until it reaches 160°F. Drain excess fat.
Stir in garlic, cumin, ancho chile, coriander and 1/2 teaspoon salt for 30 seconds. Add grated tomato and water and simmer for 5 to 6 minutes until the mixture is moist but no loose liquid remains.
Meanwhile, toss jicama and radish with lime juice and remaining salt. Keep the slaw chilled while the beef finishes.
Remove beef from the heat and let stand for 2 minutes until it stops steaming strongly. Divide among the 8 dry romaine leaves, keeping the filling along their centers.
Add a small amount of drained jicama-radish slaw to each wrap and serve immediately, 2 wraps per person.