In a 5 to 6 litre slow cooker, combine onion, capsicum, garlic, rosemary, and oregano. Crumble sausages over onion mixture. Rinse chicken and pat dry; arrange in a single layer over sausage. Sprinkle with pepper. Pour in vermouth. Cover, and cook on Low setting for 5 to 7 hours, or until chicken is tender and cooked through when pierced.
Transfer chicken to a warm, deep platter, and cover to keep warm.
In a small bowl, stir together corn flour and cold water. Stir into cooking liquid in slow cooker. Increase heat to High, and cover. Cook, stirring 2 to 3 times, until sauce is thickened (about 10 more minutes). Season to taste with salt. Spoon sauce over chicken, and sprinkle with parsley.