The Main Roads WA data such as https://catalogue.data.wa.gov.au/dataset/mrwa-road-network per the Australian Data Sources page at https://wiki.openstreetmap.org/wiki/Australian_Data_Sources#Western_Australia shows it may be used since it is CC BY 4.0 and Main Roads WA completed the OSMF LWG's CC BY waiver at https://wiki.openstreetmap.org/wiki/File:OSM_CCBY_Consent-MainRoadsWA.pdf

That's sufficient for us. It's already an approved data source for OSM, and selected data is enabled by default as background layers in editors including iD and JOSM.

Landgate data https://www.landgate.wa.gov.au/location-data-and-services/discovering-landgate-data/ isn't under an open license and not can't be used for OSM.