Preheat oven to 400F and adjust oven rack to the bottom. Pat chicken dry with paper towels and place breast side-up on a wire rack in a roaster pan. Use kitchen twine to tie legs together and tuck wings under bird. Season chicken all over with salt and pepper to taste.
In a medium bowl, combine mustards, honey, rosemary, and garlic. Season sauce with salt and pepper to taste.
In a medium bowl, toss potatoes, carrots, and onion with olive oil. Season vegetables with salt and pepper to taste and arrange around chicken.
Brush half of honey mustard sauce all over chicken, reserving remaining half for later. Arrange a few rosemary sprigs around chicken and lightly cover chicken with tin foil.
Roast chicken and vegetables at 350F 60 minutes, then remove foil, and continue roasting 20-25 minutes until the thickest part of the chicken thigh registers 165F. Remove chicken from oven and brush remaining honey mustard over chicken.
Allow chicken to rest 30 minutes before carving and serving warm with vegetables. Enjoy!