'Actually — who are you?!' Iori was interrogating that girl, ignoring me as I lay rolling on the floor.
Literal
''[or rather-っていうか], you [topic-は] who is [question-なの]!?'' Floor [locative-に] rolling-[state-ている] I [object-を] ignore-[て form], Iori [topic-は] that girl [object-を] interrogating-[state-ていた].
っていうか at the start of a line means 'or rather / actually' — used to pivot the conversation. 問いただす (といただす) is a compound verb 'to interrogate, demand an answer, grill'. The narrative structure places the subject phrase (俺) being ignored earlier, then the main clause with the action on Iori. 転がっている ('is rolling / is lying rolled up') is the ~ている form marking a state.