Preheat the oven to 400 degrees F. Line a baking sheet with aluminum foil.
Rinse off the blueberries and place them on the prepared baking sheet. Roast the berries for 12 minutes, giving the pan a shake every 4 minutes for even cooking. Remove from the oven and allow to cool. Puree in a blender until smooth and set aside.
In a large bowl, vigorously whisk together the egg yolks and sugar.
Add the milk and vanilla to a saucepan on medium heat. Whisk in the crème fraîche until smooth. When the mixture is just starting to simmer (don't boil it), slowly ladle approximately half of the liquid into the yolks while whisking.
Pour the mixture back into the saucepan and turn the heat down to medium-low. Stir in a figure 8 motion with a heat-resistant spatula for several minutes until slightly thickened. Stir in roasted blueberry puree and remove from the heat. Allow to cool for several minutes, stirring periodically. Cover with plastic wrap that’s pressed directly against the liquid to prevent a skin from forming. Chill until very cold, preferably overnight.
Prepare ice cream according to the manufacturer's instructions.