In a bowl combine the rolled oats, pumpkin seeds and ground flaxseeds.
In another bowl mix together the peanut butter, cacao powder, maple syrup and vanilla extract if using.
Mix in the wet ingredients to the oat mixture. Use your fingers to combine the ingredients. You may need to add some extra moisture if it's too dry. Add a tablespoon of oat milk at a time. The mixture should come together when pressed and stay together.
Take a tablespoon of the mixture in your hands and roll together into a ball. Each ball should weigh approximately 30g.
The protein balls can be eaten at room temperature. They can be stored in an airtight container for 2 weeks in the fridge.