Combine first 6 ingredients in a medium bowl; toss well. Set aside.
Trim fat from roast. Coat a Dutch oven with cooking spray; place over medium-high heat until hot. Add roast; cook until browned on all sides. Combine tomato sauce, picante sauce, and water; pour over roast. Add onion mixture, and bring to a boil. Cover, reduce heat, and simmer 4 1/2 to 5 hours or until roast is tender.
Transfer roast to a serving platter; serve with picante sauce mixture.