Heat oil and butter together in a large saucepan. Add roasted garlic and leeks and saute 3 minutes, until leeks are soft. Add flour and stir to coat. Add brandy and simmer 2 minutes. Add broth, tomato paste and potato and bring to a boil. Boil 6 minutes, until potatoes are fork-tender. Add shrimp and clams and simmer 1 minute to heat through. Add cream and dill and simmer 1 minute. Serve with rolls, if desired.