Honestly, I can't remember any good cult-based movies that were out around the time of Roanoke in 2014, but with all the mention of A24...I don't think it's that unrealistic to say that this *may* borrow some themes from Midsommar, considering it's popularity.
All just speculation, but it's not a secret that some originals feel basically like IPs without the branding (Seeds of Extinction) and the A24-mindset would bring a fresh approach to the "gory cannibals/cultists" trope that was never fully successful in the past.