Hi Trevor. Are you sure this is Balta spuria? All other specimens have wings & all on ALA have wings, see .. https://bie.ala.org.au/species/https://biodiversity.org.au/afd/taxa/83f2dce7-2974-4ba5-8aa1-337a58c9c068#gallery
I looked at all cockroaches expected here, and based on shape, colour, form, pronotum and pattern narrowed it down to Balta spuria or Elipsidion. I couldn't figure which it was but realised it wasn't Elipsidion based on leg colour pattern, so it must be B, spuria. I could be wrong. About the wings, nymphs will not have wings.