Grilled Tri-tip Sandwich

Ingredients

• 2 ½ -3 lb. tri-tip roast
• 1 tbsp. cooking oil
• 1 tbsp. kosher salt
• 1 tbsp. pepper
• 1 tbsp. garlic powder
• 1 tbsp. smoked paprika
• 2 tsp. onion powder
• 1 tsp. dried rosemary
• 1/3 c. red wine vinegar
• 1/3 c. olive oil
• 2 tbsp. whole grain mustard
• 4 crusty sub rolls
• favorite brand creamy horseradish sauce
• 2 red onions, caramelized
• 8 slices favorite cheese