The package trait could also be used on but you should adjust some things to make everything work.
Because the trait introduces a new relation your base model needs a primary key - we will use an auto-increment id column. If you want to use an UUID string column or another key you have to set/adjust more things (tell the model and trait which is your primary key, adjust migration ...) but even this is possible.
RoleUser.php
use Illuminate\Database\Eloquent\Relations\Pivot;
use Astrotomic\Translatable\Contracts\Translatable as TranslatableContract;
use Astrotomic\Translatable\Translatable;
class RoleUser extends Pivot implements TranslatableContract
{
use Translatable;
public $incrementing = true;
}