Heat olive oil in a large skillet over medium heat; add garlic, anchovy fillets (if using), and crushed red pepper. Cook, stirring, until anchovy breaks down and garlic is just golden, 30 to 60 seconds.
Add chicken sausage; increase heat to medium-high. Cook, stirring occasionally, until opaque, 3 to 5 minutes.
Add raisins and as much broccoli rabe to skillet as will fit; season with salt and pepper. Cook, tossing and adding remaining broccoli rabe as there is room; cook until broccoli rabe is tender, 6 to 10 minutes (less if it has been blanched).
Season with salt, pepper, and lemon juice to taste. Serve.