This question is worded very specifically so think carefully about the wording before you answer. The description for booming blade goes as follows:
You brandish the weapon used in the spell’s casting and make a melee attack with it against one creature within 5 feet of you. On a hit, the target suffers the weapon attack’s normal effects and then becomes sheathed in booming energy until the start of your next turn. If the target willingly moves 5 feet or more before then, the target takes 1d8 thunder damage, and the spell ends.
If the damage roll made by the weapon also counts as a damage roll for the spell, then the damage roll would also be under the effects of things like the elemental adept feat since elemental adept specifies that the spell has to deal that damage and not the damage roll.
When you gain this feat, choose one of the following damage types: acid, cold, fire, lightning, or thunder. Spells you cast ignore resistance to damage of the chosen type. In addition, when you roll damage for a spell you cast that deals damage of that type, you can treat any 1 on a damage die as a 2.
Does it apply to the damage roll of the weapon or only the bonus thunder damage?