1. In a medium bowl, mix the eggs with the crème fraîche, chives, tarragon and mustard; season with salt and cayenne.
2. Spread the salmon slices on a work surface. Mound 1 1/2 tablespoons of the egg salad on the short ends. Top with a few radish sticks and roll into tight cylinders. Cover and refrigerate until chilled, at least 20 minutes. Trim the ends and cut the rolls in half. Garnish with the remaining radishes and serve.
Make Ahead: The rolls can be refrigerated overnight.