Cut both the fresh and smoked fish into 1-inch cubes. Place the fish in a food processor and process for a few seconds, until you have a rough puree. Transfer to a bowl.
Stir the lemon juice, crème fraîche, and dill into the salmon. Gently crush the pink peppercorns in your hand and add them to the mousse. Gently stir the roe into the mousse, being careful not to break the fragile eggs.