Place a medium saute pan over medium heat. Add butter and maple syrup and once it melts, add rosemary, salt and cinnamon and let come together for 2 minutes until rosemary is fragrant. Remove from heat and pour butter mixture over the sweet potatoes, using a brush to get in the crevices of all the potatoes.
Place in oven to bake for 1 hour and 30 minutes.
Once the sweet potatoes have cooked, remove them from the oven and turn the oven up to 400 degrees. In a bowl, mix together all the ingredients for the toppings until combine. Pour the nut mixture along the outside of the dish on top of the sweet potatoes then place back in the oven to bake for 15 more minutes.