Heat the griddle to medium-high heat. Spread olive oil and a little sea salt evenly over the griddle.
Cut the lemons in half and set aside.
Rinse the filets and pat dry with a paper towel. Generously season each side with sea salt and black pepper and set on a sheet pan.
Pat the shrimp and scallops dry. Season with sea salt, black pepper and lemon juice, and add to the sheet pan.
Rinse the salmon and pat dry. Generously season with sea salt, black pepper, lemon juice and Old Bay, and add to the sheet pan.
Season the asparagus with garlic salt and black pepper, and add to the sheet pan.
Rinse the lobster tails. Cut through the center of the shell down the middle of each tail, flip and do the same on the bottom, then cut the lobster in half with a sharp knife. Season with a little sea salt and pepper and add to the sheet pan.
Add the food to the griddle in this order: filets, asparagus, scallops, shrimp, salmon and lobster tails. Place the lemons cut side down around the griddle and flip them when they start to turn dark brown.
Grill the filets for 5 to 6 minutes per side, or to your desired doneness. Top with garlic butter, remove and add to the platter.
Grill the asparagus for 5 to 7 minutes, or until tender.
Grill the scallops for 2 to 3 minutes per side, until golden brown.
Grill the shrimp for 2 to 3 minutes per side, until bright pink.
Grill the salmon for 6 to 8 minutes per side, depending on the thickness of the fillet.
Grill the lobster flesh side down for approximately 5 to 7 minutes, then flip.
Squeeze the roasted lemon over the asparagus, scallops, shrimp, salmon and lobster tails. Top the shrimp, scallops and salmon with garlic butter.
Arrange everything on the platter, garnish with parsley and rosemary, and serve.