Er... I'm confused now. Is he saying that you roll 1d4+1 (plus Empowered Evocation) once, and then apply that same damage total to each missile? That's the only way I can make sense out of Crawford's tweets. But that seems like a highly unintuitive reading of the text of the spell; the obvious reading is that you roll for each missile.
Without some clarification, I'm going to ignore Twitter and go with the official errata: You get your Int bonus on one damage roll, meaning one missile.
Yes, he's saying you roll once for the spell (1d4+1) and all missiles do that damage that you rolled that one time, and each one of those missiles if you're an Evoker do +X Int bonus damage.