In a large mixing bowl, combine rolled oats, protein powder, and cocoa powder. Stir until evenly mixed.

In a separate bowl, blend together peanut butter, honey, and a pinch of cinnamon until smooth.

Pour the wet mixture into the dry ingredients, and mix well until no dry spots remain.

Fold in dark chocolate chips and your choice of nuts or dried fruit until evenly distributed.

With clean hands, take small portions of the mixture and roll them into bite-sized balls.

Chill the formed protein balls on a baking sheet lined with parchment paper for at least 30 minutes.