To find the unit rate price per ounce for Rosie's hot chocolate, you need to divide the total price by the total number of ounces.
The total price is $5.00, and the total volume is 20 ounces.
\[ \text{Unit rate price per ounce} = \frac{\text{Total price}}{\text{Total ounces}} = \frac{5.00}{20} \]
Now, calculate the division:
\[ \frac{5.00}{20} = 0.25 \]
So, the unit rate price per ounce for her hot chocolate is $0.25 per ounce.