Prepare oven: Preheat oven to 450°F with oven rack 8 inches from heat.
Cook sausage: Heat oil in a large ovenproof skillet over medium-high. Add sausage, and cook, stirring to crumble, until browned and no longer pink, 6 to 7 minutes.
Add marinara sauce: Add marinara sauce and 1 cup water; bring to a boil for 2 to 3 minutes, stirring and scraping the bottom of the skillet.
Add ravioli: Cook, stirring often and gently, until sauce thickens and ravioli is just tender, 3 to 5 minutes.
Assemble lasagna: Remove from heat. Transfer half of ravioli mixture to a bowl. In skillet, layer half the mozzarella over remaining mixture, top with the set-aside ravioli mixture, then the remaining mozzarella.
Bake lasagna: Bake until cheese is melted and lightly browned, about 10 minutes. Sprinkle with basil and serve.