Final answer:
The rough woodlouse is an invertebrate because it belongs to the category of arthropods, which are characterized by their exoskeleton and jointed limbs.
Step-by-step explanation:
Invertebrates do not have a backbone, unlike vertebrates. The rough woodlouse is an invertebrate because it falls into the category of arthropods, which are a type of invertebrate. Arthropods, such as insects and spiders, are characterized by their exoskeleton and jointed limbs. Therefore, the rough woodlouse is classified as an invertebrate.