Sirloin Steak Sandwiches with Horseradish Sauce

Ingredients
For the Sirloin Steaks
4 teaspoons kosher salt
2 teaspoons paprika
2 teaspoons freshly ground black pepper
1 teaspoon garlic powder
1 teaspoon oregano
1/2 teaspoon cayenne pepper
3-4 pound sirloin beef roast
8-10 kaiser buns or other soft white bun
Sliced sweet onions
Bread and butter pickles

Horseradish Sauce 
1/2 cup fresh ground horseradish
1/2 cup mayonnaise
1 clove garlic minced or pressed
1/2 lemon juiced
pinch of cayenne
kosher salt and freshly ground black pepper