For the soft serve: Peel the bananas, cut them into chunks and freeze them, at least 1 hour. Blend the frozen bananas in a food processor until smooth. Add the raspberries and blend again until combined. Transfer to a freezer-safe container and freeze until firm, about 20 minutes.
For the chocolate shell: Blend the coconut oil, cocoa powder, maple syrup and salt in a food processor or small bowl until smooth.
To assemble the bon bons: Scoop the frozen soft serve into 1 1/2-inch balls. Dip the soft serve into the chocolate shell mixture. Place the bon bons on a baking sheet and place them back in the freezer to set, about 20 minutes.