Roommates kid

My roommate has a kid. They have decided with their co-parent that child is responsible enough to stay home for 5-6 hours at a time when necessary. Co-parent owns their own home and lives only with child. Roommate obviously has adult roommates.

My question is - if the kid gets hurt while “home alone” but a roommate is home, could the adult in the house get in any trouble? Is there implied responsibility?

Location: WA

Author: strawberry222xx_