Red’s kinda tricky, but you want to go into the Image Preprocessing tab and specify the colors in there. The IPP2 setting is the one to pay attention to. That’s their new color conversion thing. You should be able to just say “Scene Linear / Red Wide Gamut” and the r3d file in flame will convert itself.
With other files the conversion luts live inside of Flame’s Color Management node. With R3D they’re in the Image Preprocessing area.
Tags won’t convert any of the pixel values.