Juice one lemon and set juice aside. Slice the other lemon into wedges or half slices.
Preheat the oven to 425°.
Line a cookie sheet with sides with parchment paper (or foil).
Cut potatoes in half.
In a bowl, add 1 T olive oil and potatoes and 1/2 t salt and 1/2 t pepper. Mix well to coat.TIP: I use olive oil in a sprayer to coat evenly. Add potatoes to the cookie sheet in an even layer and bake for about 25 minutes until the potatoes begin to brown. I turned then with cut edges down to brown them.
Cut tops off of three garlic heads.
While potatoes are baking, cut corn in small wedges. Add corn and garlic heads to the mixing bowl with another T olive oil and 1/2 t salt and 1/2 t pepper. Mix to coat.
Add them to the sheet with the potatoes. Roast for another 15 minutes in the oven.
Cut kielbasa or sausage into slices.
In a small bowl, stir together the minced garlic, lemon juice, melted butter and Old Bay.
Remove the sheet pan from the oven and top with the kielbasa or sausage. Add back to the oven and roast for another 10 minutes.
Remove pan from oven and spread shrimp evenly over pan. TIP: Time saving to buy shrimp already cooked, deveined and peeled. If frozen, thaw slightly to save cooking time. Drizzle with the butter mixture and roast in the oven until the shrimp are no longer pink if you are using uncooked shrimp, or hot if using frozen shrimp. About 5 to 10 minutes.
To evenly coat all of the butter mixture, scoop sheet pan contents into a large serving dish or Dutch oven and then carefully lift the remaining juices up in parchment paper and pour over all of the cajun shrimp mixture. Stir to coat everything.
Serve immediately with fresh lemon wedges. Don't forget to squeeze out the garlic goodness and add to toasted french bread!