Preheat oven to 350°F.
In a pot of salted boiling water, cook the lasagna according to the directions on the package. Once cooked, drain well and lay flat on a dish or cutting board.
Heat olive oil over medium heat in a large non-stick pan or skillet. Add the turkey, onion, Cajun seasoning, and garlic. Cook while breaking up the turkey into smaller pieces until it is browned and the onion is soft. Taste and adjust the seasoning with salt and more Cajun if needed.
Add diced tomatoes and scallions. Drain off any excess liquid and stir in ricotta cheese. Set aside. Season with salt to taste.
In a saucepan over-medium low heat, melt the butter. Add flour and cook and stir for 1 minute. Gradually whisk in milk. Bring to a simmer for a few minutes to thicken. Remove sauce from heat and stir in mozzarella until melted.
Grease a casserole dish or small oven safe vessel with non-stick spray (I use a small oven safe baking dish for the portions I'm making. You don't want extra space or the filling will ooze out).
Spread about 1/4-1/2 cup of the filling on each lasagna noodle and carefully roll up. Place in prepared baking dish seam-side down. If any filling falls out, just tuck it back in. (The roll-ups should be very close together.) If there is extra filling spoon it on top.
Pour the cheese sauce evenly on top. Sprinkle with Pepper Jack cheese. Bake for 15-20 minutes, until the cheese is melted.
Let sit for 2-3 minutes. Serve with bread and garnish with scallions.