Cannot implicitly convert type 'x.role' to 'system.collections.generic.list

this my modelview .

    public class RoleAccess
{
    public int id { get; set; }
    public string name { get; set; }
    public List<ChildRole> children { get; set; }
}

and this is ChildRole :

public class ChildRole
{
    public int id { get; set; }
    public int parentid { get; set; }
    public string name { get; set; }

}

now i need to fill view model with this code :

    public List<RoleAccess> SubRole()
{
    List<RoleAccess> sub = new List<RoleAccess>();
    foreach (var parent in Roles.Where(x => x.Id == 0))
    {
        foreach (var child in Roles.Where(x=>x.RoleLevel==parent.Id))
        {
            sub.Select(role=>new RoleAccess
            {
                id = parent.Id,
                name = parent.Description,
                children=child
            });
        }
    }
    return sub;
}

but it show me this error in this line :

Cannot implicitly convert type 'StoreFinal.Entities.Entities.Identity.Role' to 'System.Collections.Generic.List

How Can i solve This Problem ????