I think Britt was abducted by a local she didn't know; that said I think the ROC crew might know something or have knowledge of who. Like someone else said there is no other reason that would really make sense for them to avoid giving statements or much to LE.
It is hard to say what involvement they might have but they sure act guilty. I'm not just speaking about the boys. I think the girls behavior is even worse.
I wish the investigators would re-interview this bunch! Also, with all the survelliance on the street when Britt was walking you'd think someone would have picked up on something- be it a van pulling up, or one of the girls/guys from her group, something....