Place a saucepan on your stove at a medium heat. Put milk and flour into the saucepan and stir until the mixture becomes a paste-like consistency.
Add vanilla extract and stir into the mixture.
Remove the saucepan from the heat and allow it to fully cool before moving onto the next step.
In a bowl, whisk together the sugar and butter until light and fluffy.
Once the flour-milk-vanilla mixture has reached room temperature, add the sugar-butter mixture into the saucepan. It is best to use an electric whisk to fully combine both of these mixtures together.
Spread your icing onto cinnamon rolls and dig in!