Sprinkle each steak with salt on both sides. Gently press the coffee grounds, brown sugar and cayenne pepper into both sides of the steak. Place in a large ziplock bag and marinate in the refrigerator for at least 2 hours.
Preheat oven to 350 degrees F.
Arrange the baguette slices on a large rimmed baking sheet. Brush each slice with olive oil, and season with a pinch of garlic powder and coarse salt. Bake for 10 minutes.
Heat 1 tablespoon olive oil to a large pan. Sear the steak on both sides for 4 minutes each. Remove from the pan and cover on a plate, resting for 10 minutes. Thinly slice the steak against the grain.
Arrange a few leaves of arugula on each toasted baguette slice, followed by two slices of steak, and a slice of Roth Horseradish Havarti cheese. Bake the crostini for another 5-10 minutes, until the cheese is melted. Garnish with extra arugula leaves and serve immediately.