Stir together the milk, ½ cup of the half and half, and the Torani Sugar-Free Almond Roca Syrup in a dutch oven over medium-low heat stirring occasionally. Cook for 15 minutes, being careful not to bring to a boil. Remove from heat.
Beat the eggs in a large bowl. Gradually stir half of the hot milk mixture into the egg mixture, and then add the egg mixture to the remaining hot milk mixture in the Dutch oven.
Cook over medium-low, occasionally stirring for 20 to 25 minutes. The temperature should reach 160° F. Strain and add in the rum, vanilla, and cinnamon. Whisk to combine.
Cover and chill for 1 hour.
Beat the remaining 1 cup of heavy cream with an electric mixture over high until soft peaks form.
Serve the eggnog with a dollop of whipped cream and a sprinkle of cinnamon.