Trim fat from roast. In a small bowl, combine fennel seed, garlic powder, and pepper; rub into roast on all sides. In a 4- or 5-quart slow cooker, combine fennel, carrot, and onion. Place roast on top, cutting roast to fit, if necessary. Pour pasta sauce over roast in cooker.
Cover and cook on low-heat setting for 9 to 10 hours or on high-heat setting for 4 1/2 to 5 hours. Remove roast from cooker and cut into serving size pieces. Remove vegetables with a slotted spoon and serve along side the roast. Remove sauce mixture and skim off any fat; set aside.
Toss hot cooked pasta with parsley. Serve roast, vegetable mixture and skimmed sauce with pasta mixture.
Got to be a typo, there's no way 6 oz of dry pasta is enough to go with 8 servings of pot roast. I think it's 16 oz, i.e., the whole pound box of penne. Does no one proofread these things?