Preheat oven to 425F. Toss broccolini with 1 1/2 Tbsp olive oil, spread on sheet pan, and roast 15-20 minutes until browned and tender.
Bring large pot of salted water to boil. Cook pasta according to package directions. Reserve 3/4 cup pasta water before draining.
Heat 1 1/2 Tbsp olive oil in large pan over medium heat. Add sausage rounds and brown 9-10 minutes, flipping halfway.
Push sausage aside, add remaining 1 Tbsp oil to center of pan, then add garlic. Sauté 1 minute until fragrant and stir into sausage.
Pour marinara into pan and bring to gentle simmer. Cook until pasta is ready.
One minute before pasta is done, stir half-and-half into sauce.
Add drained pasta, Pecorino, and basil to pan and toss to coat. Add reserved pasta water as needed to thin sauce.
Fold in roasted broccolini and serve with crushed red pepper if desired.